Added possibility to skip the login form fields page.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | ---
| Fixed tickets | ---
| Refs tickets  | #900
| License       | MIT
| Doc PR        | ---

This adds the ability for authentication modules to avoid one of the user's clicks for a new account registration.