Adds handling the format property ($request['format'] ) in the class WP_REST_Posts_Controller.

Adds handling the format property ($block->context['query']['format'])  in the function build_query_vars_from_query_block.

…er::test_registered_query_params

…oken logic

In `build_query_vars_from_query_block`, the variable that contains the format attribute had the wrong name, which caused a PHP warning. The variable name was updated to `$formats`.

One of the if-statements was closed incorrectly, which meant that all the logic for handling the format property was not used. Because of this, the wrong posts showed in the query loop block on the front of the site.
The closing curly bracket for the if-statement was moved to solve this.

One additional check was added to the wrapping if-statement:
It now checks that `$block->context['query']['format']` is not empty, and is an array, before running the rest of the code.

Generated an updated fixture in `wp-api-generated.js` by running the PHPUnit tests.
The update adds `format` to `mockedApiResponse.Schema`

… post formats.

`WP_REST_Posts_Controller`: remove unnecessary array conversion for the `format` parameter.
This addresses feedback that was left on the Gutenberg pull request.

… to `$query_params['format']`

In `WP_REST_Posts_Controller` `get_collection_params` class method; add `uniqueItems` to the `$query_params['format']` array.

The purpose is to require all items in the array to be unique.
This will help manage user errors, if duplicate items are passed in the `format` parameter.

This change addresses feedback left on the Gutenberg pull request.

Adds the regenerated fixtures which includes `uniqueItems` in the `format` array in `mockedApiResponse.Schema`.

The fixture was regenerated by running the PHPUNit tests.

Use multiline comments instead of multiple single line comments.

In the `build_query_vars_from_query_block` function and the `WP_REST_Posts_Controller` class, a query with the `NOT EXISTS` operator is used to exclude all items that have a post format assigned.

This commit removes a `terms` parameter from the two queries, because the terms are redundant when `NOT EXISTS` is used.

When querying for the `format` property in the `build_query_vars_from_query_block` function and the `WP_REST_Posts_Controller` class, the query may be combined with other taxonomy queries. For example, the user may expect the result to be posts with a specific format and a specific category.

Previously, the `relation` parameter in the query was set to `OR`, which should return items that has either the format or the taxonomy.

This commit changes the `relation` to `AND` with the intention to limit the result to items that have both the queried taxonomy and the format.

Validate the that the `format` property passed to the query using the block context is either the default (standard) or a supported post format, registered with `add_theme_support()`.

Compare `format` to the supported formats in  `get_post_format_slugs()` and remove invalid formats.

…en querying for the `format`

When querying for the `format` property in the `WP_REST_Posts_Controller` class,  the `relation` parameter in the query was incorrectly set to `AND`.
This commit changes the relation back to `OR`.

This is needed because when a user queries for a combination of the `standard` post format and any other format, the result should include items with either the given format, or no format (standard).
A post item can not have more than one format.

The commit also renames the variable `$tax_query` to `$formats_query` to improve the readability.

…g for the `format`

When querying for the `format` property in `build_query_vars_from_query_block`, the `relation` parameter in the query was incorrectly set to `AND`.
This commit changes the relation back to `OR`.

This is needed because when a user queries for a combination of the `standard` post format and any other format, the result should include items with either the given format, or no format (standard).
A post item can not have more than one format.

The commit also renames the variable `$tax_query` to `$formats_query` to improve the readability.

This commit corrects inline docBlocks, removes unnecessary string concatenations, and tries to resolve a PHP coding standard issue about the formatting of an array.

When querying for formats, the relation between the format and other taxonomies like categoryíes and tags should be `AND`.

The intention is to allow users to query for a post with a specific category and a specific format.