The config.json file can live in a number of places. In my configuration it is at the top of the .wiki folder:
We share an example of our configuration for wiki to show how to set it up so all subdomains are owned by the same owner.
We notice where important server files get installed. See also Wiki Admin, Wiki Relocation
While exploring wiki and kubernetes, your author discovered his own incorrect assumptions about the behavior of wikiDomains configuration. Here we describe what we were expecting—expressed as a goal for improved configuration code. We also consider changing cli.coffee and farm.coffee from coffee-script to es6 javascript.
It is possible to configure a wiki on a per-site basis using a configuration fie.
By default wiki will, if we don't configure a security module, make all content read-only. github 
Configuring each OAuth provider requires two steps: i) regestering our wiki installation, as an app, with the OAuth provider, and ii) configuring Federated Wiki to use the shared secrets created.
GitHub only allows the configuration a single authorization callback URL for each OAuth application, so you will been to create an OAuth application for each wiki domain - github
The cincludes google specific advice on how to configure that service to work with wiki. readme
Create an application with Twitter Application Management .