CheckForJSON makes sure that the request's Content-Type is application/json.

GetHTTPErrorStatusCode retrieve status code from error message.

MatchesContentType validates the content type against the expected one.

NewStatusError returns a error object with HTTP status code.

ParseForm ensures the request form is parsed even with invalid content types.

UserFromContext returns the authenticated user from the context using UserKey.

VersionFromContext returns an API version from the context using APIVersionKey.

WriteError decodes a specific error and sends it in the response.

WriteJSON writes the value to the http response stream as json with standard json encoding.

APIVersionKey is the client's requested API version.

UseKey is the key for userdb.User values in Contexts.

APIFunc is an adapter to allow the use of ordinary functions as API endpoints.