feat: support third party orm to interact with go-zero (#1286)

* fixes #987

* chore: fix test failure

* chore: add comments

* feat: support third party orm to interact with go-zero

* chore: refactor

zrpc/resolver/internal/resolver_test.go

@@ -0,0 +1,37 @@
+package internal
+
+import (
+	"testing"
+
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/serviceconfig"
+)
+
+func TestNopResolver(t *testing.T) {
+	// make sure ResolveNow & Close don't panic
+	var r nopResolver
+	r.ResolveNow(resolver.ResolveNowOptions{})
+	r.Close()
+}
+
+type mockedClientConn struct {
+	state resolver.State
+}
+
+func (m *mockedClientConn) UpdateState(state resolver.State) error {
+	m.state = state
+	return nil
+}
+
+func (m *mockedClientConn) ReportError(err error) {
+}
+
+func (m *mockedClientConn) NewAddress(addresses []resolver.Address) {
+}
+
+func (m *mockedClientConn) NewServiceConfig(serviceConfig string) {
+}
+
+func (m *mockedClientConn) ParseServiceConfig(serviceConfigJSON string) *serviceconfig.ParseResult {
+	return nil
+}