feat: Add proto definition for UDF input.

This represents the input in server code or RPC request. i.e., the RPC request will contain these for clients to pass input to UDFs.

Bug: 303835821
Change-Id: Ie38c44f0b66dad20fcf1ce9c17e40c1fc6dffee8
GitOrigin-RevId: 670aa81de2b79fc1348c07240d1244211c203fce

public/BUILD

@@ -63,3 +63,16 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+proto_library(
+    name = "api_schema_proto",
+    srcs = ["api_schema.proto"],
+    deps = [
+        "@com_google_protobuf//:struct_proto",
+    ],
+)
+
+cc_proto_library(
+    name = "api_schema_cc_proto",
+    deps = [":api_schema_proto"],
+)

public/api_schema.proto

@@ -0,0 +1,55 @@
+// Copyright 2022 Google LLC
+//
+// 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 kv_server;
+
+import "google/protobuf/struct.proto";
+
+// This file contains types that may be used in either request/response or UDF.
+// This is always the first argument to the UDF and is the only argument that
+// the KV server is not oblivious to. Example use cases are to pass server side
+// flags or parameters.
+message UDFExecutionMetadata {}
+
+// Context useful for logging and debugging requests compatible with the Bidding
+// and Auction service.
+message LogContext {
+  // UUID for the request (as originating from client).
+  string generation_id = 1;
+  string adtech_debug_id = 2;
+}
+
+message ConsentedDebugConfiguration {
+  bool is_consented = 1;
+  string token = 2;
+}
+
+// Represents one argument to UDF. One UDF invocation may have multiple
+// arguments. The actual meaning and number of the arguments are defined by the
+// specific use case of the KV server. i.e., different use cases will have API
+// overlay which will specify the argument spec. UDF authors is responsible of
+// writing the UDF to conform to the use case specific API.
+//
+// If `tags` is not empty, the argument will be passed to the UDF
+// with 2 fields: "tags" and "data". Otherwise, the content of `data` will be
+// directly passed as the argument.
+message SingleUDFArgument {
+  // optional. Metadata about the data.
+  google.protobuf.ListValue tags = 1;
+
+  // required. Data of the input argument.
+  google.protobuf.Value data = 2;
+}