metadatahandler: Expose method scope and operation
We log a bunch of gRPC information via the metadatahandler
package. In
several contexts though we have been wishing for rough classifiers of
gRPC methods so that we can for example easily filter for all methods
that mutate a repository.
Introduce two new fields:
- "grpc.meta.method_operation" denotes whether the RPC is an
accessor-, mutator- or maintenance-style RPC.
- "grpc.meta.method_scope" denotes whether the RPC is repository- or
storage-scoped.
With this it becomes a lot simpler to filter full categories of RPCs.
Closes #5450 (closed).
Edited by Patrick Steinhardt