Opt-in to AuthService

[eevdev]

Please describe your use case / problem.
I have a setup where an Emissary-ingress is shared with multiple services. To support auth for some of those services I could introduce an AuthService, but that would then enable it for all the ones that don't need it, unless adding bypass_auth: true to all other Mappings.

Enabling AuthService for some services shouldn't break or put to risk other services.

Describe the solution you'd like
Option to opt-in to the AuthService instead of opt-out.

Being able to set the default value for bypass_auth to true would work, so that those services that need auth have to opt-in by setting it to false. The Helm chart should also support this option.

Describe alternatives you've considered
Add bypass_auth: true to all other Mappings, including adding support for that to all relevant Helm charts etc.

Additional context
Related to #174

[gecube]

I had the same thoughts. Another option is to configure and / or rewrite auth-service itself creating an allow-list of FQDNs and endpoints which will be protected by authentication (or otherwise - skipped). The drawback is that all traffic will still go to auth-service and if it fails all services not requiring authentication will be unavailable.