REST API: Add uniqueItems as a permitted endpoint argument JSON Schema keyword.

Support for the `uniqueItems` keyword was added in [48357], but wasn't included in the list of permitted keywords for `WP_REST_Controller::get_endpoint_args_for_item_schema()`. This prevented the keyword from being automatically supported if specified in a controller's item schema.

Props TimothyBlynJacobs.
Merges [48796] to the 5.5 branch.
Fixes #51021.

git-svn-id: https://develop.svn.wordpress.org/branches/5.5@48807 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/rest-api/endpoints/class-wp-rest-controller.php

@@ -645,6 +645,7 @@ abstract class WP_REST_Controller {
 			'pattern',
 			'minItems',
 			'maxItems',
+			'uniqueItems',
 		);
 
 		foreach ( $schema_properties as $field_id => $params ) {

tests/phpunit/tests/rest-api/rest-controller.php

@@ -265,7 +265,7 @@ class WP_Test_REST_Controller extends WP_Test_REST_TestCase {
 
 		$this->assertArrayHasKey( 'items', $args['somearray'] );
 
-		foreach ( array( 'minItems', 'maxItems' ) as $property ) {
+		foreach ( array( 'minItems', 'maxItems', 'uniqueItems' ) as $property ) {
 			$this->assertArrayHasKey( $property, $args['somearray'] );
 		}
 

tests/phpunit/tests/rest-api/rest-test-controller.php

@@ -101,13 +101,14 @@ class WP_REST_Test_Controller extends WP_REST_Controller {
 					'default' => 'a',
 				),
 				'somearray'      => array(
-					'type'     => 'array',
-					'items'    => array(
+					'type'        => 'array',
+					'items'       => array(
 						'type' => 'string',
 					),
-					'minItems' => 1,
-					'maxItems' => 10,
-					'context'  => array( 'view' ),
+					'minItems'    => 1,
+					'maxItems'    => 10,
+					'uniqueItems' => true,
+					'context'     => array( 'view' ),
 				),
 				'someobject'     => array(
 					'type'                 => 'object',