* Makes Omniauth rely on Proc instead of initializer value for redirect uri
* Adds SiteConfig.app_domain test for OAuth providers callback_url generation
* Fixes protocol mismatch in test
* Fixes URL encoding problem with query params in test
* Sets Omniauth full_host config to match the environment
* Fixes tests by passing missing params in omniauth env to mocks
* Default param as nil in omniauth mock helpers