Changes to Register media upload

the media_type request property type changed from string to no type

the request required property media_type became not write-only

removed subschema #1 from the response body allOf list for the response status 201

added the non-success response with the status 400

added the non-success response with the status 401

added the non-success response with the status 403

added the non-success response with the status 404

added the non-success response with the status 429

added the optional property upload_parameters to the response with the 201 status

added the optional property upload_url to the response with the 201 status

added the required property media_id to the response with the 201 status

added the required property media_type to the response with the 201 status

added the success response with the status 200

the response's body type changed from no type to object for status 201

endpoint added