Starts a named OAuth2 login flow other than the client's default one. It triggers the configured oauth2 client's normal login redirect internally, then rewrites the Location header and the body of that redirect so the browser is sent to triggerFlow instead of the client's defaultFlow, merging in any configured login parameters.
Parameters added to the login redirect. A loginParameter with a value contributes that constant, one without forwards the incoming request's query parameter of the same name, if it is present.