Add Usage proto file

Define an upload RPC to allow usage reports to be uploaded to the
content service.

Author: Andrew Farries

components/content-service-api/usage.proto

@@ -0,0 +1,23 @@
+// Copyright (c) 2022 Gitpod GmbH. All rights reserved.
+// Licensed under the GNU Affero General Public License (AGPL).
+// See License-AGPL.txt in the project root for license information.
+
+syntax = "proto3";
+
+package contentservice;
+
+option go_package = "github.com/gitpod-io/gitpod/content-service/api";
+
+service UsageReportService {
+  // UploadURL provides a URL to which clients can upload the content via HTTP PUT.
+  rpc UploadURL(UsageReportUploadURLRequest) returns (UsageReportUploadURLResponse) {}
+}
+
+message UsageReportUploadURLRequest {
+  string bucket = 1;
+  string name = 2;
+}
+
+message UsageReportUploadURLResponse {
+  string url = 1;
+}