chore(v2): Fetch cache result from MLMD and put cache result into argo output artifacts/parameters

api/Makefile

@@ -1,7 +1,13 @@
 PROTO_PATH=/usr/local/include/
 
-gen_proto: v2alpha1/pipeline_spec.proto
+gen_pipeline_spec_proto: v2alpha1/pipeline_spec.proto
 	cd v2alpha1 && protoc -I=$(PROTO_PATH) -I=. \
 		--go_out=go \
 		--go_opt=paths=source_relative \
 		pipeline_spec.proto
+
+gen_cache_key_proto: v2alpha1/cache_key.proto
+	cd v2alpha1 && protoc -I=$(PROTO_PATH) -I=. \
+		--go_out=go \
+		--go_opt=paths=source_relative \
+		cache_key.proto

api/v2alpha1/cache_key.proto

@@ -0,0 +1,38 @@
+// Copyright 2021 The Kubeflow Authors
+//
+// 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";
+
+option go_package = "github.com/kubeflow/pipelines/api/v2alpha1/go";
+package ml_pipelines;
+
+import "google/protobuf/any.proto";
+import "pipeline_spec.proto";
+
+message CacheKey {
+  map<string, ArtifactNameList> inputArtifactNames = 1;
+  map<string, Value> inputParameters = 2;
+  map<string, RuntimeArtifact> outputArtifactsSpec = 3;
+  map<string, string> outputParametersSpec=4;
+  ContainerSpec containerSpec=5;
+}
+
+message ContainerSpec {
+  string image = 1;
+  repeated string cmdArgs = 2;
+}
+
+message ArtifactNameList {
+  repeated string artifactNames = 1;
+}