Add: Add original_source and author_text to the templates rest API.

[jorgefilipecosta]

For the new "All templates" UI to work properly we need the REST API to provide to additional fields original_source, and author_text.
This ticket tracks its addition to the core.

It ports the following PRs from the Gutenberg repository:
​https://github.com/WordPress/gutenberg/pull/56333
​https://github.com/WordPress/gutenberg/pull/56567
​https://github.com/WordPress/gutenberg/pull/56990

GitHub PR for the patch at ​https://github.com/WordPress/wordpress-develop/pull/5940.

This PR adds the fields author_text and original source to the template rest API.
Backports into the core ​https://github.com/WordPress/gutenberg/pull/56333/, ​https://github.com/WordPress/gutenberg/pull/56567/, and ​https://github.com/WordPress/gutenberg/pull/56990.

[jorgefilipecosta]

In 57366:

Editor: Add original_source and author_text to the templates REST API.

For the new "All templates" UI to work properly we need the REST API to provide to additional fields original_source, and author_text.

Props ntsekouras, get_dave.
Fixes #60358.

Committed at ​https://github.com/WordPress/wordpress-develop/commit/400a7ac31b79411ed69751810d35a4391cd6e132.

[kebbet]

Please milestone this ticket to 6.5 since [57366] was committed to trunk during this milestone period. Thanks @gefilipecosta!

[jorgefilipecosta]

In 57374:

Coding Standards: Remove unnecessary access and internal annotations from two functions in WP_REST_Templates_Controller.

This commit removes unnecessary access and internal annotations from two functions that are private and as such don't require the annotation. It also adds the since annotation with the 6.5 release given that the annotation may be useful.

Props swissspidy.
See #60358.

[david.binda]

Sorry for re-opening the ticket, but I have noticed a minor issue in the modified PHPUnit tests introduced in r57374 .

The newly expected original_source and author_text fields should have more appropriate message passed to the assertArrayHasKey method, but have a copy of the message used for the parent field.

See the attached diff.

[swissspidy]

In 57710:

Tests: Update incorrect assertion message added in [57366].

Props david.binda.
Fixes #60358.