[Security] Added a missing field in SimpleAuthenticationHandler

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Added tests and made a small CS fix as a bonus.

Btw, the properties are protected. Do we really want to provide extension points here?