fix: revert federation filed from proto message to ensure back-compat…

…ibility

proto/types.proto

@@ -35,7 +35,6 @@ message Ping {}
 message Pong {}
 
 message Envelope {
-  reserved 11;
   // uid is auto generated by rmb.
   string uid = 1;
   // client specific tags
@@ -62,6 +61,9 @@ message Envelope {
   // schema of the payload of either the request or the resposne message.
   optional string schema = 10;
 
+  // a federation url (domain)
+  // this filed ignored by relays but left for back compatibilty with old peers
+  optional string federation = 11;
 
   // pyload of the message is interpreted differently based
   // on the message filed

src/types/mod.rs

@@ -325,6 +325,10 @@ impl Challengeable for Envelope {
             write!(hash, "{}", schema)?;
         }
 
+        if let Some(ref federation) = self.federation {
+            write!(hash, "{}", federation)?;
+        }
+
         match self.payload {
             None => {}
             Some(types::envelope::Payload::Plain(ref data)) => {