OAuth2 (#32)

* make auth method asyncs

* oauth2 demo support

* full coverage

* update docs

package/etc/ahriman.ini

@@ -12,6 +12,8 @@ root = /
 target = disabled
 allow_read_only = yes
 max_age = 604800
+oauth_provider = GoogleClient
+oauth_scopes = https://www.googleapis.com/auth/userinfo.email
 
 [build]
 archbuild_flags =