feat(kuma-cp): implement delta xDS for envoy config exchange

api/mesh/v1alpha1/dataplane.proto

@@ -7,6 +7,7 @@ option go_package = "github.com/kumahq/kuma/api/mesh/v1alpha1";
 import "api/mesh/options.proto";
 import "api/mesh/v1alpha1/metrics.proto";
 import "api/mesh/v1alpha1/envoy_admin.proto";
+import "api/mesh/v1alpha1/envoy.proto";
 import "google/protobuf/duration.proto";
 import "google/protobuf/wrappers.proto";
 import "validate/validate.proto";
@@ -369,4 +370,7 @@ message Dataplane {
   // Deprecated: this feature will be removed for Universal; on Kubernetes, it's
   // not needed anymore.
   Probes probes = 3;
+
+  // EnvoyConfiguration provides additional configuration for the Envoy sidecar.
+  EnvoyConfiguration envoy = 4;
 }

api/mesh/v1alpha1/envoy.proto

@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+package kuma.mesh.v1alpha1;
+
+option go_package = "github.com/kumahq/kuma/api/mesh/v1alpha1";
+
+message EnvoyConfiguration {
+  enum XdsTransportProtocolVariant {
+    // This value defines default control-plane variant.
+    DEFAULT = 0;
+    // Enables incremental xDS between control-plane and the Envoy.
+    DELTA_GRPC = 1;
+    // Enables state of the world xDS between control-plane and the Envoy.
+    GRPC = 2;
+  }
+  // xDSTransportProtocol provides information about protocol used for
+  // configuration exchange between control-plane and Envoy sidecar.
+  XdsTransportProtocolVariant xds_transport_protocol_variant = 1;
+}