* Creates a single LLMS post.
	 *
	 * Extending classes can add additional object fields by overriding the method `update_additional_object_fields()`.
	 *
	 * @since 1.0.0-beta.1
	 * @since 1.0.0-beta.7 Added `"llms_rest_insert_{$this->post_type}"` and `"llms_rest_insert_{$this->post_type}"` action hooks:
	 *                     fired after inserting/updating an llms post into the database.
	 * @since 1.0.0-beta.25 Allow updating meta with the same value as the stored one.
	 * @since 1.0.0-beta.27 Handle custom meta registered via `register_meta()` and custom rest fields registered via `register_rest_field()`.
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
	 */
	public function create_item( $request ) {

		$schema = $this->get_item_schema();

		$prepared_item = $this->prepare_item_for_database( $request );
		if ( is_wp_error( $prepared_item ) ) {
			return $prepared_item;
		}

		$prepared_item = array_diff_key( $prepared_item, $this->get_additional_fields() );
		$object        = $this->create_llms_post( $prepared_item );
		if ( is_wp_error( $object ) ) {

			if ( 'db_insert_error' === $object->get_error_code() ) {
				$object->add_data( array( 'status' => 500 ) );
			} else {
				$object->add_data( array( 'status' => 400 ) );
			}

			return $object;
		}

		/**
		 * Fires after a single llms post is created or updated via the REST API.
		 *
		 * The dynamic portion of the hook name, `$this->post_type`, refers to the post type slug.
		 *
		 * @since 1.0.0-beta.7
		 *
		 * @param LLMS_Post       $object   Inserted or updated llms object.
		 * @param WP_REST_Request $request  Request object.
		 * @param array           $schema   The item schema.
		 * @param bool            $creating True when creating a post, false when updating.
		 */
		do_action( "llms_rest_insert_{$this->post_type}", $object, $request, $schema, true );

		// Set all the other properties.
		// TODO: maybe we want to filter the post properties that have already been inserted before.
		$set_bulk_result = $object->set_bulk( $prepared_item, true, true );
		if ( is_wp_error( $set_bulk_result ) ) {

			if ( 'db_update_error' === $set_bulk_result->get_error_code() ) {
				$set_bulk_result->add_data( array( 'status' => 500 ) );
			} else {
				$set_bulk_result->add_data( array( 'status' => 400 ) );
			}

			return $set_bulk_result;
		}

		$object_id = $object->get( 'id' );

		$additional_fields = $this->update_additional_object_fields( $object, $request, $schema, $prepared_item );
		if ( is_wp_error( $additional_fields ) ) {
			return $additional_fields;
		}

		if ( ! empty( $schema['properties']['featured_media'] ) && isset( $request['featured_media'] ) ) {
			$this->handle_featured_media( $request['featured_media'], $object_id );
		}

		$terms_update = $this->handle_terms( $object_id, $request );
		if ( is_wp_error( $terms_update ) ) {
			return $terms_update;
		}

		$meta_update = $this->update_meta( $object, $request, $schema );
		if ( is_wp_error( $meta_update ) ) {
			return $meta_update;
		}

		// Fields registered via `register_rest_field()`.
		$fields_update = $this->update_additional_fields_for_object( $object, $request );
		if ( is_wp_error( $fields_update ) ) {
			return $fields_update;
		}

		$request->set_param( 'context', 'edit' );

		/**
		 * Fires after a single llms post is completely created or updated via the REST API.
		 *
		 * The dynamic portion of the hook name, `$this->post_type`, refers to the post type slug.