Split up the caching tests as prep for adding a new cache store. Slices
the mega test/caching_test.rb into behavior modules, concrete store
tests, and cross-cutting store tests.

Considering moving cache store behavior modules into lib/ so they may be
used for acceptance testing by third parties.

[ci skip] Add backquote to :counter_cache option

Ensure MSSQL password uses real ENV var.

[ci skip] Fix another link in active_record_postgresql.md

Fix link in active_record_postgresql.md [ci skip]

remove the extra comma in association_basics.md [ci skip]

That won't be true for Action Pack and Action Mailer.

Bundle capybara 2.14.1 that includes fix for Ruby warnings

Ref: https://github.com/teamcapybara/capybara/pull/1868

Remove unreachable code

`Time.find_zone!` raise `ArgumentError` if invalid value is specified.
https://github.com/rails/rails/blob/379a0b42daf0d8e14130db7fd886d05d8d88e3f2/activesupport/lib/active_support/core_ext/time/zones.rb#L97..L99

Therefore, the return value never becomes nil.

form_with requires people to pass an id manually, so users can just
prefix their namespace right there.

Forgot all about https://github.com/rails/rails/pull/28844/files#r113780934

cc @rafaelfranca

Rails.cache.write_multi foo: 'bar', baz: 'qux'

Plus faster `fetch_multi` with stores that implement `write_multi_entries`.
Keys that aren't found may be written to the cache store in one shot
instead of separate writes.

The default implementation simply calls `write_entry` for each entry.
Stores may override if they're capable of one-shot bulk writes, like
Redis `MSET`.

Update upgrading guide w.r.t. Parameters to use other example method …

Update upgrading guide w.r.t. Parameters to use other example method than slice as this has actually been implemented by Parameters

PostgreSQL 10 converts unknown type to text type

Commit 1a5d9399 removed the "Profiling Rails Applications" guide
but the YAML entry for this guide wasn't.

[ci skip]

Remove redundant `assert_nothing_raised` before another assertions

- Rename test cases from  `unknown` to `unrecognized` since unknown OID
is one of possible unrecognized types by Rails

- Use "select 'pg_catalog.pg_class'::regclass" whose OID is 2205, which
will not be converted to recognized type in PostgreSQL 10.

activerecord_unittest=# select oid, typname from pg_type where oid in (2205, 2277);
 oid  | typname
------+----------
 2205 | regclass
 2277 | anyarray
(2 rows)

Addresses #28868

Fix `test_pluck_without_column_names` when using Oracle

Remove html tag making markdown misrender [ci skip]

These `assert_nothing_raised` are covered by following assertions.

Testing `ReservedWordTest` for all adapters

Other examples were removed in 53ff5fc6

[ci skip]

`ReservedWordTest` expects that any identifiers are quoted properly.
It should be tested for all adapters.