Add OpenID Connect login support (#77)

* Add OpenID Connect login support
* Add docs for OIDC config with Google Auth
* Use Google styles for log in
- Add support for linking existing account
- Force users to sign-in with passoword first, when linking existing accounts
- Add support to create new user when using OIDC
- Add identities to user to prevent account take-ver
- Make tests mocking instead of being integration tests
- Manage session handling correctly
- use OmniAuth.config.mock_auth instead of passing auth data via request env
* Conditionally render Oauth button

- Set a config item `configuration.x.auth.oidc_enabled`
- Hide button if disabled

---------

Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>
Signed-off-by: soky srm <sokysrm@gmail.com>
Co-authored-by: sokie <sokysrm@gmail.com>

test/fixtures/oidc_identities.yml

@@ -0,0 +1,21 @@
+bob_google:
+  user: family_admin
+  provider: openid_connect
+  uid: google-uid-12345
+  info:
+    email: bob@bobdylan.com
+    name: Bob Dylan
+    first_name: Bob
+    last_name: Dylan
+  last_authenticated_at: <%= 1.day.ago %>
+
+jakob_google:
+  user: family_member
+  provider: openid_connect
+  uid: google-uid-67890
+  info:
+    email: jakobdylan@yahoo.com
+    name: Jakob Dylan
+    first_name: Jakob
+    last_name: Dylan
+  last_authenticated_at: <%= 2.days.ago %>