#Extraction Reference
Supported handler inputs:
-`RequestContext`-`Path<T>`-`Query<T>`-`Option<Query<T>>`-`Header<T>`-`Option<Header<T>>`-`QueryMap`-`BodyBytes`-`TextBody`-`JsonBody<T>`-`RequestState<T>`-`Option<RequestState<T>>`-`IdentityState<T>`-`Option<IdentityState<T>>`Behavior:
-invalid request binding maps to request-level `400` responses
- middleware can attach identity with `RequestContext::insert_identity(value)`- middleware can attach typed per-request state with `RequestContext::insert_state(value)`- cloned `RequestContext` values share request-local state and identity storage
-`JsonBody<T>` and `TextBody` participate in route contract checks before handler execution
- handler parameters are intentionally limited to request-derived values; application dependencies belong on `self`