[nginx] Set proper Basic Auth realm with Advanced ACLs

[StephanTexxpro]

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Is your feature request related to a problem? Please describe. When I enable the Advanced ACLs, the Realm for the Basic Auth is always set to the hardcoded string 'OPNsense Protected Area - Authentication Required'. As the Basic Auth Realm defines (according to my understanding of RFC 7235) a protection space, sharing the same realm for many (proxied) websites seems to be problematic.

Describe the solution you'd like Take the value of the already available field 'Basic Authentication' within the 'Location' form, pass it to ngx_auth.php and change the hardcoded string dynamicly to the value passed.

Describe alternatives you've considered N/A

Additional context N/A