Why middleware applied at blueprint level applies to whole application ?

Hello,

When I'm declaring a middleware with: `my_blueprint.register_middleware(func_middleware)`,
I've found that the middleware applies to the application, not only the blueprint.

So i've searched on the github repo and see that actually when we use `blueprint.register_middleware` it seems to cal the same method on app level,

I found this strange as if we use blueprint, technically we also need to defined resources / middlewares only at blueprints level.

Should such a feature (to have blueprint scoped middlewares) may be introduced to chalice ?

Start by tracing how blueprint.register_middleware delegates to the application-level middleware method. Compare the intended blueprint scope with the current application-wide behavior. Done means a blueprint middleware affects only that blueprint's resources, with coverage for both blueprint and application routes.

Written by the indexing model from the issue text.