*Motivation*

Currently producers uses `System.currentTimeMillis()` as publish timestamp by default.
However at some use cases, producers would like to a different way for generating publish timestamp.
E.g. in a database use case, a producer might be use HLC (Hybrid Logic Clock) as publish timestamp;
in integration tests, it might require the producer to use a deterministic way to generate publish timestamp.

*Changes*

This PR introduces a `clock` in building the client. This allows applications to override the system clock
with its own implementation.

*Verify the change*

Add unit test to test customized clock in both batch and non-batch cases.

### Motivation

Improve the documentation for Non-Persistent Topic

### Modifications

* Improve error codes and error messages
* Description Information of Improvement Parameters

### Motivation
User can create tools on bookkeeper using ManagedLedger factory which provides [constructor](https://github.com/apache/pulsar/blob/master/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerFactoryImpl.java#L121) to create ml-factory using self-managed bookkeeper (it's not used by broker).
So, in case of self-managed bk-client, ML-Factory couldn't shutdown it gracefully and we see issue: #4573

### Modification
- ML-Factory creates `DefaultBkFactory` to create self-managed bk-client and shutdowns same bk-client while closing the resource. 

* Refactoring Function Component implementation

* cleaning up

Fix license header check error by apache-rat.

*Motivation*

Currently the schema data is only validated in compatibility checker. If the schema data is uploaded from admin api, there is no validation if the schema is the first version.

*Changes*

Add schema data validator to validate the schema data before storing it in schema storage.

### Motivation
When writing Pulsar docs, we can adopt a consistent writing styles, whoever the author is.
Here I introduce [Google Developer Documentation Style Guide](https://developers.google.com/style/) for Pulsar technical docs. The style guide generally conforms to with most popular technical writing styles, such as *IBM style guides*, *Microsoft style guide*, *The Chicago Manual of Style*, and so on.
In addition, *Google Developer Documentation Style Guide* is open to all, and the link is easy to share among all participants.

### Modifications
1. Restructure the content of the site2/reademe file: website, doc, and translation.
2. Introduce *Google Developer Documentation Style Guide* in **Contribute to documentation**.

### Motivation
- debezium-postgres connector is missing in distribution (build)

### Modifications
- assemby updated

### Motivation

Add document for java client to describe how to use each subscription modes and the difference between each subscription modes.

### Modifications

Add subscription modes section for java client doc.

### Does this pull request potentially affect one of the following parts:

*If `yes` was chosen, please highlight the changes*

  - Dependencies (does it add or upgrade a dependency): (no)
  - The public API: (no)
  - The schema: (no)
  - The default values of configurations: (no)
  - The wire protocol: (no)
  - The rest endpoints: (no)
  - The admin cli options: (no)
  - Anything that affects deployment: (no)

### Documentation

  - Does this pull request introduce a new feature? (no)

Signed-off-by: Nxiaolong.ran <ranxiaolong716@gmail.com>

Update message backlog figures in the database when clearing/deleting subscriptions. Keeping the UI up to date pending the next collector run. (#4559)

Motivation
When a subscription's backlog is cleared or the subscription is deleted the UI doesn't reflect the change in the backlog until the next run of the collector. This change updates the database with the new backlog count at the subscription and topic level.

Modifications
If the deletion of a subscription has a 204 response reduce the topic's message backlog count by the amount on the subscription.
If the clearing of a subscription has a 204 response reduce the topic's message backlog count by the amount on the subscription and reduce the subscriptions backlog count to 0.

*Motivation*

- The code for encoding and decoding key/value schema is spreading over multiple places.
- Make code changes to prepare supporting key/value schema in AUTO consumers
- Make schema tools display key/value schema in a pretty format

*Modifications*

- Move the common logic of encoding and decoding key/value schema to a common class KeyValueSchemaInfo
- Expose the common class in DefaultImplementation so that it can be available for public usage
- Fix the display problem on displaying key/value schema

*Verify this change*

- Add bunch of the unit tests for key/value schemas

### Motivation
Improve doc on Pulsar Functions.

### Modifications
1. Add an example of Pulsar Function for Go.
2. Add Pulsar Functions SDK: Go.
3. Add an example of Go function logging.
4. Refine a section title from "Parallelism" as "Run instances in parallel"
5. Refine some typos.

### Documentation

  - Does this pull request introduce a new feature? (yes )
  - If yes, how is the feature documented? ( docs)

### Motivation

Introduce batch message container framework to support multiple ways to do message batch. 
Currently, pulsar support a most basic batch message container, use the batch message container framework can quickly implement other types batch message container, even users can customize their own batch message container.

Add a new batch message container named BatchMessageKeyBasedContainer to support batching message in key_shared subscription mode.

Support pulsar scripts to work with bookkeeper

Pulsar already have been supported multi host. Introduce them in Pulsar document.

## Motivation
Improving the quality of the documentation.

`Tenant`, `namespace` and `sourceName` already appear in `PathParam` and shouldn't be a part of `sourceConfigJson`.

*Motivation*

In gitsha b7a56773 , it introduced a provided dependency for pulsar-storm-test, which it will fail release process. Since it will attempt to transfer the pom file for  `com.twitter:carbonite:pom:1.5.0` which is a dependency comes from storm-server.

*Changes*

Make all the dependencies scoped at test scope for two test modules. So maven release will not attempt to release them.

*Motivation*

KafkaProducerInterceptorWrapper uses a LongDeserializer for retrieve deserializer

*Modifications*

Fix the bug

*Verify this change*

Add unit test to cover the convertion

* Do not strip ExecutionException from the stack trace

### Motivation
While add "Write and run a Go function" section, improve doc on Pulsar Functions: quick start throughout.

### Modifications

1. Add a section of "Write and run a Go function".
2. Update the the first-person pronoun as the second-person pronoun.
3. Correct the usage of "Pulsar Functions" and "a Pulsar function". For the usage discussion, see #4507 .
4. Change the future tense into present tense.
5. Refine part of structure (heading level).
6. Refine sentences to be more clear and concise.
7. Refine some typos.

### Documentation

  - Does this pull request introduce a new feature? (yes)
  - If yes, how is the feature documented? ( docs) 

Master Issue: #2664

Motivation:
Add acknowledgeMessage, commit, abort for transaction in PersistentSubscription.

Changes:
Will put message in Pending_ACK status when acknowledgeMessage is called with TxnID.
No real status class introduced, only added collection to hold messages in Pending_ACK status.
Current PR only keep Pending_ACK state in memory, in subsequent PR will also persistent these pending acks so we can recover from broker failure.

Add commitTxn to put message to Deleted status.
Add abortTxn to put message to Pending status.

For normal acknowledgeMessage and redeliverUnacknowledgedMessages, will check to see if 
message if message is in Pending_ACK first. If true, will **ignore** those acks/redeliverys.

Add unit test.

### Motivation

Make sure we record charset in the properties. So that we know which charset to be used for encoding and decoding strings.

### Modifications

Add charset to the properties 

* revisit documentation for pulsar admin api

* format

* update json body

* sinkConfig as doc base

* [improve doc] Update source rest api doc
Signed-off-by: Nxiaolong.ran <ranxiaolong716@gmail.com>

* fix comments
Signed-off-by: Nxiaolong.ran <ranxiaolong716@gmail.com>

* fix comments
Signed-off-by: Nxiaolong.ran <ranxiaolong716@gmail.com>

### Motivation

This is the 4th and last (implementation) change for pip-33. 

It includes reading and caching the last N snapshots and sending the updates to the other clusters.

Previous PRs: 
 1. #4299
 2. #4340
 3. #4354

* Feature - reset cursor on Reader to current position

*Motivation*

There are some cases in which is it useful to be able to include current
position of message when reset of cursor was made.

This was reported by a `vvy` on slack, no issue has been created to track this.

*Modifications*

  - Add startMessageIdInclusive() to support include current position of
    reset on ReaderBuilder.
  - Add resetIncludeHead field for Reader and Consumer Configuration Data
  - Fix position of cursor for non durable consumer.
  - Improve discard if statement for batch enable mode.
  - Add discard if statement for batch disable mode.
  - Improve test case for latest Reader seek.
  - Add test case to assert the start of specific message id at the expected
    position with data provider scenarios:
      A. Batch enable and start inclusive enable.
      B. Batch enable and start inclusive disable.
      C. Batch disable and start inclusive enable.
      D. Batch disable and start inclusive disable.

* add docs on how to debug Pulsar Functions

* adding to sidebar

* Apply suggestions from code review
Co-Authored-By: NAnonymitaet <50226895+Anonymitaet@users.noreply.github.com>

* addressing comments and rewording

* adding comma

* addressing comments

* fixing minor issue