[Route Groups] Implement IApplicationBuilder to support grouped middleware

[halter73]

We want MapGroup to support middleware via the IApplicationBuilder interface so things like UseResponseCompression(), UseHttpLogging(), UseForwardedHeaders(), UseRequestLocalization(), terminal middleware like UseStaticFiles() and more can be called on a group.

Describe the solution you'd like

This still needs design, but there are a lot of open questions. We still need to figure out how we define a middleware that runs every time a route handler in a given group is hit. before running the endpoint and similar middleware from inner groups?

• How do we deal with middleware that checks the request path?
  • Can we trim the group prefix from the path?
• What about middleware that's aware of grouping and wants the real full path?
  • Do we add a new feature to support this?
  • Can middleware use default endpoint metadata ([Route Groups] Add default metadata to endpoints exposing group structure #41429) to infer the real full path?
• What if no endpoint is matched, but the middleware would have been terminal?
  • Do we create a low-priority catchall endpoint with the route prefix?
• Then what if the middleware isn't terminal?
  • Can we still fallback to the normal missing endpoint logic if we add a fake catchall endpoint?
• Will we support middleware rewriting the route after matching a specific group prefix and rerun routing?
  • This seems like too much. What if the new

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We're moving this issue to the .NET 7 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
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