Message protobuf schema

message Message {
    string id = 1;
    oneof content {
	    … 
    }
}

message PrePrepare {
    View uint64 = 1;
    Seq uint64 = 2;
    Payload bytes = 3;
    Header bytes = 4;
    Metadata bytes = 5;	
}



message Prepare {
    View uint64 = 1;
    Seq uint64 = 2;
    Digest bytes = 3;
}


message Commit {
    Digest bytes = 1;
    Error string = 2;
    Signature bytes = 3; 
}