feat: support http->http in gateway (#4605)

gateway/config.go

@@ -12,14 +12,22 @@ type (
 		Upstreams []Upstream
 	}
 
+	// HttpClientConf is the configuration for an HTTP client.
+	HttpClientConf struct {
+		Target  string
+		Prefix  string `json:",optional"`
+		Timeout int64  `json:",default=3000"`
+	}
+
 	// RouteMapping is a mapping between a gateway route and an upstream rpc method.
 	RouteMapping struct {
 		// Method is the HTTP method, like GET, POST, PUT, DELETE.
 		Method string
 		// Path is the HTTP path.
 		Path string
-		// RpcPath is the gRPC rpc method, with format of package.service/method
-		RpcPath string
+		// RpcPath is the gRPC rpc method, with format of package.service/method, optional.
+		// If the mapping is for HTTP, it's not necessary.
+		RpcPath string `json:",optional"`
 	}
 
 	// Upstream is the configuration for an upstream.
@@ -27,12 +35,14 @@ type (
 		// Name is the name of the upstream.
 		Name string `json:",optional"`
 		// Grpc is the target of the upstream.
-		Grpc zrpc.RpcClientConf
+		Grpc *zrpc.RpcClientConf `json:",optional"`
+		// Http is the target of the upstream.
+		Http *HttpClientConf `json:",optional=!grpc"`
 		// ProtoSets is the file list of proto set, like [hello.pb].
 		// if your proto file import another proto file, you need to write multi-file slice,
 		// like [hello.pb, common.pb].
 		ProtoSets []string `json:",optional"`
-		// Mappings is the mapping between gateway routes and Upstream rpc methods.
+		// Mappings is the mapping between gateway routes and Upstream methods.
 		// Keep it blank if annotations are added in rpc methods.
 		Mappings []RouteMapping `json:",optional"`
 	}