chore: add license header (#35)

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

go/greptime/v1/ddl.pb.go

@@ -1,3 +1,17 @@
+// Copyright 2023 Greptime Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
 // 	protoc-gen-go v1.28.1
@@ -20,8 +34,9 @@ const (
 	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
 )
 
-// "Data Definition Language" requests, that create, modify or delete the database structures but not the data.
-// `DdlRequest` could carry more information than plain SQL, for example, the "table_id" in `CreateTableExpr`.
+// "Data Definition Language" requests, that create, modify or delete the
+// database structures but not the data. `DdlRequest` could carry more
+// information than plain SQL, for example, the "table_id" in `CreateTableExpr`.
 // So create a new DDL expr if you need it.
 type DdlRequest struct {
 	state         protoimpl.MessageState