[REQ] [Swift6] requiresAuthentication should be optional or enum with type of authorization

Is your feature request related to a problem? Please describe.

According to the OpenAPI documentation, it's possible to create a "path" with security options: without authorization + with authorization (the behavior of the "path" depends on this).
I encountered a similar need.

Describe the solution you'd like

• Provide option requiresAuthentication as enum

enum RequiresAuthentication {
    case required
    case optional
    case nonRequired
}

for determine when we need to force check auth in interceptor or not.

• May be we also need to provide types of auth for choose properly way of auth in interceptor

• I suppose, also we need to improve algorithms in generator, because now it don't understand more then one auth variants

Describe alternatives you've considered

There is a hack solution, for example, looking at the method name in the interceptor and making a decision manually )))
But this is not code generation way :)

Additional context

No files or tests are named. Start by tracing how the Swift6 generator handles requiresAuthentication, authentication interceptors, and multiple OpenAPI security variants; clarify the expected optional or enum behavior and supported authorization types. Done means generated clients correctly distinguish required, optional, and non-required authentication cases.