ReportRateLimit Metrics

[eguzki]

A new gRPC method was introduced in #439

service RateLimitService {
  // The report method modifies specific counters associated with the descriptors, incrementing each one by the amount specified in $hits_addend$
  rpc Report(envoy.service.ratelimit.v3.RateLimitRequest) returns (envoy.service.ratelimit.v3.RateLimitResponse); 
}

Should we add custom metrics (i.e. report_calls) for the new gRPC service method? Currently we have (relevant ones):

# HELP authorized_calls Authorized calls
# TYPE authorized_calls counter
authorized_calls{limitador_namespace="test_namespace"} 19

# HELP limited_calls Limited calls
# TYPE limited_calls counter
limited_calls{limitador_namespace="test_namespace"} 1