invitation process upgrade

pb/messages.proto

@@ -30,7 +30,15 @@ message Invitation {
   string uuid          = 6; // invitation uuid
   int64  expiry        = 7; // the server allowed expiry date, it may be smaller than the requested timeout according to server policy
   int32  step          = 8; // progress in the invitation process : 1=initiator pub key, 2=invited data enc with pub key, 3=initator data full encrypted, 4=invited All OK !
-  string from          = 9; // used in step 1 the public key to encrypt step 2 message
+  string from          = 9; // still useful ?
+}
+
+// This payload migh be used for file serialization as well as Invitation/payload in case of through server invitation
+message InvitationInitPayload {
+  string uuid               = 1; // uuid of the invitation, it is set here on init cause the payload might be encrypted
+  string name               = 2; // name of the initiator
+  string public_key         = 3; // public key to be used for step 2 encryption
+  string invitation_message = 4; // message for the invited peer
 }
 
 // structure for requesting incoming messages