Use FullName for service route generation (#601)

Use the protobuf runtime's `FullName` rather than our own, bug-prone
implementation.

Fixes #597.

---------

Co-authored-by: Akshay Shah <akshayjshah@users.noreply.github.com>

cmd/protoc-gen-connect-go/main.go

@@ -425,7 +425,7 @@ func generateServerConstructor(g *protogen.GeneratedFile, service *protogen.Serv
 		}
 		g.P(")")
 	}
-	g.P(`return "/`, reflectionName(service), `/", `, httpPackage.Ident("HandlerFunc"), `(func(w `, httpPackage.Ident("ResponseWriter"), `, r *`, httpPackage.Ident("Request"), `){`)
+	g.P(`return "/`, service.Desc.FullName(), `/", `, httpPackage.Ident("HandlerFunc"), `(func(w `, httpPackage.Ident("ResponseWriter"), `, r *`, httpPackage.Ident("Request"), `){`)
 	g.P("switch r.URL.Path {")
 	for _, method := range service.Methods {
 		g.P("case ", procedureConstName(method), ":")
@@ -510,10 +510,6 @@ func procedureHandlerName(m *protogen.Method) string {
 	return fmt.Sprintf("%s%sHandler", unexport(m.Parent.GoName), m.GoName)
 }
 
-func reflectionName(service *protogen.Service) string {
-	return fmt.Sprintf("%s.%s", service.Desc.ParentFile().Package(), service.Desc.Name())
-}
-
 func isDeprecatedService(service *protogen.Service) bool {
 	serviceOptions, ok := service.Desc.Options().(*descriptorpb.ServiceOptions)
 	return ok && serviceOptions.GetDeprecated()