feat: restful -> grpc gateway (#2155)

* Revert "chore: remove unimplemented gateway (#2139)"

This reverts commit d70e73ec66.

* feat: working gateway

* feat: use mr to make it faster

* feat: working gateway

* chore: add comments

* feat: support protoset besides reflection

* feat: support zrpc client conf

* docs: update readme

* feat: support grpc-metadata- header to gateway- header conversion

* chore: add docs

gateway/requestparser_test.go

@@ -0,0 +1,48 @@
+package gateway
+
+import (
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/zeromicro/go-zero/rest/pathvar"
+)
+
+func TestNewRequestParserNoVar(t *testing.T) {
+	req := httptest.NewRequest("GET", "/", nil)
+	parser, err := newRequestParser(req, nil)
+	assert.Nil(t, err)
+	assert.NotNil(t, parser)
+}
+
+func TestNewRequestParserWithVars(t *testing.T) {
+	req := httptest.NewRequest("GET", "/", nil)
+	req = pathvar.WithVars(req, map[string]string{"a": "b"})
+	parser, err := newRequestParser(req, nil)
+	assert.Nil(t, err)
+	assert.NotNil(t, parser)
+}
+
+func TestNewRequestParserNoVarWithBody(t *testing.T) {
+	req := httptest.NewRequest("GET", "/", strings.NewReader(`{"a": "b"}`))
+	parser, err := newRequestParser(req, nil)
+	assert.Nil(t, err)
+	assert.NotNil(t, parser)
+}
+
+func TestNewRequestParserWithVarsWithBody(t *testing.T) {
+	req := httptest.NewRequest("GET", "/", strings.NewReader(`{"a": "b"}`))
+	req = pathvar.WithVars(req, map[string]string{"c": "d"})
+	parser, err := newRequestParser(req, nil)
+	assert.Nil(t, err)
+	assert.NotNil(t, parser)
+}
+
+func TestNewRequestParserWithVarsWithWrongBody(t *testing.T) {
+	req := httptest.NewRequest("GET", "/", strings.NewReader(`{"a": "b"`))
+	req = pathvar.WithVars(req, map[string]string{"c": "d"})
+	parser, err := newRequestParser(req, nil)
+	assert.NotNil(t, err)
+	assert.Nil(t, parser)
+}