start implementing gw serve mux support

pkg/srv/grpc/grpc.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"strings"
 
+	"github.com/grpc-ecosystem/grpc-gateway/runtime"
 	"github.com/rs/zerolog"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
@@ -23,10 +24,15 @@ type appGRPCServer struct {
 	serverOpts   []grpc.ServerOption
 	logger       *zerolog.Logger
 	server       *grpc.Server
+	gatewayMux   *runtime.ServeMux
 	shutdownFunc func(context.Context) error
 	doneChan     chan error
 }
 
+func (g *appGRPCServer) GetMux() *runtime.ServeMux {
+	return g.gatewayMux
+}
+
 // Returns a shutdown func, a channel indicating done / error,
 // and an up-front error if server fails to start
 func InitGRPCServer(ctx context.Context, opts *opts.GRPCOpts) (