[Security] Added 'host' option to firewall configuration

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7103
| License       | MIT
| Doc PR        | 

I'm not particularly fond of all the `isset()` checks, and would rather set default values for the `pattern` and `host` options (to `null`). However I'm not sure if that would have any other impact.