rpc: expose graph synced status within GetInfo

lnrpc/rpc.proto

@@ -1343,6 +1343,9 @@ message GetInfoResponse {
 
     /// The color of the current node in hex code format
     string color = 17 [json_name = "color"];
+
+    // Whether we consider ourselves synced with the public channel graph.
+    bool synced_to_graph = 18 [json_name = "synced_to_graph"];
 }
 
 message Chain {

lnrpc/rpc.swagger.json

@@ -2218,6 +2218,11 @@
         "color": {
           "type": "string",
           "title": "/ The color of the current node in hex code format"
+        },
+        "synced_to_graph": {
+          "type": "boolean",
+          "format": "boolean",
+          "description": "Whether we consider ourselves synced with the public channel graph."
         }
       }
     },