addAction method
Serves action at POST path, which defaults to '/${action.name}'.
contextProvider builds the action context from the request (typically
from auth headers); throwing from it rejects the request.
Paths match exactly, so /hello and /hello/ would be different routes.
To avoid that trap, a trailing / is rejected (except for / itself).
Throws an ArgumentError if path doesn't start with /, ends with
/, or is already registered on this router.
Implementation
void addAction(
Action action, {
String? path,
ContextProvider? contextProvider,
}) {
addRoutes(this, [
(action: action, path: path ?? '/${action.name}'),
], contextProvider: contextProvider);
}