Changes to Log an external Call activity

added the pattern property ^custom\.(cf|lcf|ccf|acf|gcf|scf)_[A-Za-z0-9]+$ to the response body for the status 200

added the pattern property ^custom\.(cf|lcf|ccf|acf|gcf|scf)_[A-Za-z0-9]+(\.(add|remove))?$ to the request body

removed the pattern property ^custom\. from the request body

added the media type application/json for the response with the status 400

added the media type application/json for the response with the status 401

added the non-success response with the status 403

added the non-success response with the status 429

removed the non-success response with the status 404

added the pattern property ^custom\. to the request body

removed the request property custom_fields

removed the request property created_by_id

added the new optional request property created_by