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.

resources/sass/_buttons.scss

@@ -99,6 +99,9 @@ button {
     fill: var(--color-primary);
   }
 }
+.text-button.hover-underline:hover {
+  text-decoration: underline;
+}
 
 .button.block {
   width: 100%;