Provide HandlerAspect context via env instead of function param (#2488)

[987Nabil]

This PR is a different way of solving #2488 that seems to me to be superior to #2553

With this PR, the context provided by a HandlerAspec is no longer injected via the function param if a handler/Handler.fromFunction but instead via the environment. So users would just require context via ZIO.serviceX.
The implementation is such, that h: Handler[Env with Ctx, _, _, _] @@ aspect: HandlerAspect[_, Ctx] would eliminate the Ctx from the env of the handler. The aspect may add new Env requirements as well. Only for partial Env providing in Scala 2, an explicit param needs to be handed over to @@. For all other cases inference works fine.

This change also enables auth context to be handed over to handlers of endpoint API implementations, since it does not require the context to be known while creating the endpoint. There is an example in the added tests.

This seems to be the most consistent way to provide context via an aspect that works for all use cases

• single handler
• Routes
• Endpoint API

fixes #2488
/claim #2488

[khajavi]

By the changes in this PR, we can move bearerAuthWithContext to apply it to the whole routes on line 72 💯

[guersam]

It's just what I have been wanted, thanks for the work, @987Nabil :D

Providing context via environment has a great DX benefit that attaching a middleware in the future doesn't break existing handlers' interface.

Also, as one of the primary use case for this is authentication, there are many endpoints that don't care of the exact user identity but as long as the user is authenticated. This implementation enables mixing two types of endpoints seamlessly .

[jdegoes]

Nice work! You're going to make a lot of people happy!