multi: add channel open parameters to channel acceptor

Add more fields to channel acceptor response so that users can have more
fine grained control over their incoming channels. With our chained
acceptor, it is possible that we get inconsistent responses from
multiple chained acceptors. We create a conjugate repsponse from all the
set fields in our various responses, but fail if we get different, non-
zero responses from our various acceptors. Separate merge functions are
used per type so that we avoid unexpected outcomes comparing interfaces
(panic on comparing types that aren't comparable), with casting used
where applicable to avoid code duplication.

chanacceptor/chainedacceptor.go

@@ -50,6 +50,8 @@ func (c *ChainedAcceptor) Accept(req *ChannelAcceptRequest) *ChannelAcceptRespon
 	c.acceptorsMtx.RLock()
 	defer c.acceptorsMtx.RUnlock()
 
+	var finalResp ChannelAcceptResponse
+
 	for _, acceptor := range c.acceptors {
 		// Call our acceptor to determine whether we want to accept this
 		// channel.
@@ -61,11 +63,31 @@ func (c *ChainedAcceptor) Accept(req *ChannelAcceptRequest) *ChannelAcceptRespon
 		if acceptorResponse.RejectChannel() {
 			return acceptorResponse
 		}
+
+		// If we have accepted the channel, we need to set the other
+		// fields that were set in the response. However, since we are
+		// dealing with multiple responses, we need to make sure that we
+		// have not received inconsistent values (eg a csv delay of 1
+		// from one acceptor, and a delay of 120 from another). We
+		// set each value on our final response if it has not been set
+		// yet, and allow duplicate sets if the value is the same. If
+		// we cannot set a field, we return an error response.
+		var err error
+		finalResp, err = mergeResponse(finalResp, *acceptorResponse)
+		if err != nil {
+			log.Errorf("response for: %x has inconsistent values: %v",
+				req.OpenChanMsg.PendingChannelID, err)
+
+			return NewChannelAcceptResponse(
+				false, errChannelRejected, nil, 0, 0,
+				0, 0, 0, 0,
+			)
+		}
 	}
 
 	// If we have gone through all of our acceptors with no objections, we
 	// can return an acceptor with a nil error.
-	return NewChannelAcceptResponse(true, nil)
+	return &finalResp
 }
 
 // A compile-time constraint to ensure ChainedAcceptor implements the