Is your feature request related to a problem? Please describe.
Gotify logs the client IP address by using only the remote IP address.
But if the requests comes from a reverse proxy, the only IP logged is the reverse proxy IP address.

Describe the solution you'd like
Reverse proxies typically add headers like X-Forwarded-For containing the real client IP address.
It should be optional though because if there's no reverse proxy, a client may forge a fake X-Forwarded-For header. Gotify can't determine by itself alone if there's a reverse proxy, so the configuration should be explicit.

Describe alternatives you've considered
Viewing the reverse proxy logs instead of gotify logs, but it's not as convenient.

Additional context
None