Improved ActiveRecord Connection Pool docs [ci skip]

Removed mocha from Active Record Part 2

[ci skip]

Don't hardcode table name

The schema_migrations table name is configurable. We should use this value when checking for ignored table names when dumping schema instead of a hardcoded value.

Ref #21618

[ci skip]

Update documentation to remove 'desirable' suggestion for what is not a clear cut approach

Improved explanation of the <script> tag CSRF behavior

[ci skip] Remove `DEFAULT NULL` from examples

Use rack.session_options instead of directly change env

Doc SchemaMigration class.

this commit removes some direct access to `env`.

This commit is to abstract the code away from the env hash.  It no
longer needs to have the routes key hard coded.

Bundler tzinfo-data in windows, even first generated new app are Mac

Fix undefined method error on exception

Update Validation guide for acceptance method

This will make the Gemfile.lock be dirty in some environments

This changes the renderer class to store the controller and defaults as
an instance variable rather than allocating a new class.  You can create
a new renderer with an new env by calling `Renderer#new` or use new
defaults by calling `Renderer#with_defaults` and saving the return value
somewhere.

Also I want to keep the `env` private since I would like to change the
keys in the future.  This commit only translates particular keys that
the user requested.

this means the reader doesn't need to lock, but does have the added cost
of a new object created for every controller

The controller class is shared among threads, so we need to lock when
allocating the Renderer.

Remove methods that are never invoked

Fix doc of limit option for a text column [ci skip]

Follow up #21591.

The document of limit option for a text column is incorrect.

MySQL: the limit is byte length, not character length
Pg, Sqlite3: variable unlimited length

Fix HSTS default expire in ActionDispatch::SSL docs.

Fixes #21122 - does not change any current behavior; simply reflects
the fact that two conditions of the if/else statement are never reached.

The reason is #17227 which adds a default terminator to AS::Callbacks.

Therefore, even callback chains that do not define a terminator now
have a terminator, and `chain_config.key?(:terminator)` is always true.

Of course, if no terminator was defined, then we want this new default
terminator not to do anything special. What the terminator actually does
(or should do) is discussed in #21218 but the simple fact that a default
terminator exists makes this current PR valid.

*Note* that the conditional/simple methods have not been removed in
AS::Conditionals::Filter::After because of `:skip_after_callbacks_if_terminated`
which lets a user decide **not** to skip after callbacks even if the chain was
terminated.

fix typo intance -> instance in ActionView [ci skip]