Function: Retrieves the pixel sizes for avatars.

Function: Validate a value based on a schema.

Function: Sanitize a value based on a schema.

Function: Parses a date into both its local and UTC equivalent, in MySQL datetime format.

Function: Returns a contextual HTTP error code for authorization failure.

Function: Validate a request argument based on details registered to the route.

Function: Sanitize a request argument based on details registered to the route.

Function: Adds the REST API URL to the WP RSD endpoint.

Function: Outputs the REST API link tag into page header.

Function: Sends a Link header for the REST API.