The cincludes google specific advice on how to configure that service to work with wiki. readme 
Google provides an overview of their OAuth service and details about how they support the interaction with another server-side app like wiki. google google
Google will provide application identifying information. The wiki is configured by adding the client ID and client secret to the configuration. They need not be added inside the wikiDomains definition, as the OAuth can have multiple callbacks defined, we still need the domain definition so that the wiki security plugin can understand what is required.
{ "farm": true, "security_type": "passportjs", "google_clientID": "CLIENT ID", "google_clientSecret": "CLIENT SECRET", "wikiDomains": { "example.wiki": {} } }