rpc: Add PendingOpenChannel to SubscribeChannelEvents

This commit adds PendingOpenChannel to SubscribeChannelEvents stream in
the gRPC API.
This is useful for keeping track of channel openings that Autopilot does.
It can also be used for the non-initator side of a channel opening to keep
track of channel openings.

lnrpc/rpc.proto

@@ -1930,6 +1930,7 @@ message ChannelEventUpdate {
         ChannelCloseSummary closed_channel = 2 [ json_name = "closed_channel" ];
         ChannelPoint active_channel = 3 [ json_name = "active_channel" ];
         ChannelPoint inactive_channel = 4 [ json_name = "inactive_channel" ];
+        PendingUpdate pending_open_channel = 6 [json_name = "pending_open_channel"];
     }
 
     enum UpdateType {
@@ -1937,6 +1938,7 @@ message ChannelEventUpdate {
          CLOSED_CHANNEL = 1;
          ACTIVE_CHANNEL = 2;
          INACTIVE_CHANNEL = 3;
+         PENDING_OPEN_CHANNEL = 4;
     }
 
     UpdateType type = 5 [ json_name = "type" ];

lnrpc/rpc.swagger.json

@@ -1467,7 +1467,8 @@
         "OPEN_CHANNEL",
         "CLOSED_CHANNEL",
         "ACTIVE_CHANNEL",
-        "INACTIVE_CHANNEL"
+        "INACTIVE_CHANNEL",
+        "PENDING_OPEN_CHANNEL"
       ],
       "default": "OPEN_CHANNEL"
     },
@@ -2149,6 +2150,9 @@
         "inactive_channel": {
           "$ref": "#/definitions/lnrpcChannelPoint"
         },
+        "pending_open_channel": {
+          "$ref": "#/definitions/lnrpcPendingUpdate"
+        },
         "type": {
           "$ref": "#/definitions/ChannelEventUpdateUpdateType"
         }