Review and update of login auto initiation PR

For PR #3406

- Updated naming from 'redirect' to 'initate/initation'.
- Updated phpunit.xml and .env.example.complete files with the new
  option.
- Cleaned up controller logic a bit.
- Added content and design to the new initation view to not leave user
  on a blank view for a while.
- Added non-JS button to initiation view as fallback option for
  progression.
- Moved new test to it's own Test class and expanded with additional
  scenario tests for better functionality coverage.

phpunit.xml

@@ -29,6 +29,7 @@
     <server name="MAIL_DRIVER" value="array"/>
     <server name="LOG_CHANNEL" value="single"/>
     <server name="AUTH_METHOD" value="standard"/>
+    <server name="AUTH_AUTO_INITIATE" value="false"/>
     <server name="DISABLE_EXTERNAL_SERVICES" value="true"/>
     <server name="ALLOW_UNTRUSTED_SERVER_FETCHING" value="false"/>
     <server name="AVATAR_URL" value=""/>