Protos: Put avatar in each message type like iOS/Android

FREEBIE

protos/IncomingPushMessageSignal.proto

@@ -163,12 +163,12 @@ message GroupContext {
   optional AttachmentPointer avatar  = 5;
 }
 
+message GroupDetails {
   message Avatar {
     optional string contentType = 1;
     optional uint32 length      = 2;
   }
 
-message GroupDetails {
   optional bytes  id       = 1;
   optional string name     = 2;
   repeated string members  = 3;
@@ -177,6 +177,11 @@ message GroupDetails {
 }
 
 message ContactDetails {
+  message Avatar {
+    optional string contentType = 1;
+    optional uint32 length      = 2;
+  }
+
   optional string number  = 1;
   optional string name    = 2;
   optional Avatar avatar  = 3;