Add initial protos for GitHubService (#398)

proto/lekko/backend/v1beta1/github_service.proto

@@ -0,0 +1,35 @@
+// Copyright 2022 Lekko Technologies, Inc.
+//
+// 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.
+
+syntax = "proto3";
+
+package lekko.backend.v1beta1;
+
+// Service for interacting with GitHub in contexts such as actions, CI, etc.
+service GitHubService {
+  // Gets an access token for the Lekko GitHub app as an installation to be able to perform certain actions on GitHub.
+  // See: https://docs.github.com/en/apps/creating-github-apps/authenticating-with-a-github-app/authenticating-as-a-github-app-installation
+  rpc GetInstallationAccessToken(GetInstallationAccessTokenRequest) returns (GetInstallationAccessTokenResponse) {}
+}
+
+message GetInstallationAccessTokenRequest {
+  string team_name = 1;
+  string owner_name = 2;
+  string repo_name = 3;
+}
+
+message GetInstallationAccessTokenResponse {
+  string token = 1;
+  int64 installation_id = 2;
+}