Labels are consistently validated across services

* The combined size of a key/value pair cannot exceed 4096 bytes

Signed-off-by: Jess Valarezo <valarezo.jessica@gmail.com>

api/services/images/v1/images.pb.go

@@ -67,6 +67,7 @@ type Image struct {
 	// and do not get inherited into the package image in any way.
 	//
 	// Labels may be updated using the field mask.
+	// The combined size of a key/value pair cannot exceed 4096 bytes.
 	Labels map[string]string `protobuf:"bytes,2,rep,name=labels" json:"labels,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
 	// Target describes the content entry point of the image.
 	Target containerd_types.Descriptor `protobuf:"bytes,3,opt,name=target" json:"target"`

api/services/images/v1/images.proto

@@ -51,6 +51,7 @@ message Image {
 	// and do not get inherited into the package image in any way.
 	//
 	// Labels may be updated using the field mask.
+	// The combined size of a key/value pair cannot exceed 4096 bytes.
 	map<string, string> labels = 2;
 
 	// Target describes the content entry point of the image.