Changes to Update a GatewayConfig.

added the new optional request property custom_headers

added the optional property custom_headers to the response with the 200 status

the request property auth_mechanism became not nullable

the request property description became not nullable

the request property endpoint became not nullable

the request property name became not nullable

the auth_mechanism request property type changed from object to no type

removed the request property auth_mechanism/key

removed the request property auth_mechanism/type

added AuthMechanismView subschema #2 to the auth_mechanism request property anyOf list

endpoint added