Add http_uri proto. (#538)

Per discuss from PR: #530
Add EnvoyHttpTarget meesage

Signed-off-by: Wayne Zhang <qiwzhang@google.com>

envoy/api/v2/core/BUILD

@@ -79,6 +79,19 @@ api_go_proto_library(
     ],
 )
 
+api_proto_library(
+    name = "http_uri",
+    srcs = ["http_uri.proto"],
+    visibility = [
+        ":friends",
+    ],
+)
+
+api_go_proto_library(
+    name = "http_uri",
+    proto = ":http_uri",
+)
+
 api_proto_library(
     name = "grpc_service",
     srcs = ["grpc_service.proto"],

envoy/api/v2/core/http_uri.proto

@@ -0,0 +1,37 @@
+syntax = "proto3";
+
+package envoy.api.v2.core;
+
+import "validate/validate.proto";
+
+// Envoy external URI descriptor
+// [#not-implemented-hide:]
+message HttpUri {
+  // The HTTP server URI. It should be a full FQDN with protocol, host and path.
+  //
+  // Example:
+  //
+  // .. code-block:: yaml
+  //
+  //    uri: https://www.googleapis.com/oauth2/v1/certs
+  //
+  string uri = 1 [(validate.rules).string.min_bytes = 1];
+
+  // Specify how `uri` is to be fetched. Today, this requires an explicit
+  // cluster, but in the future we may support dynamic cluster creation or
+  // inline DNS resolution. See `issue
+  // <https://github.com/envoyproxy/envoy/issues/1606>`_.
+  oneof http_upstream_type {
+    option (validate.required) = true;
+    // A cluster is created in the Envoy "cluster_manager" config
+    // section. This field specifies the cluster name.
+    //
+    // Example:
+    //
+    // .. code-block:: yaml
+    //
+    //    cluster: jwks_cluster
+    //
+    string cluster = 2 [(validate.rules).string.min_bytes = 1];
+  }
+}