lnrpc/watchtowerrpc: add protos for GetInfo

lnrpc/watchtowerrpc/watchtower.proto

@@ -0,0 +1,28 @@
+syntax = "proto3";
+
+package watchtowerrpc;
+
+option go_package = "github.com/lightningnetwork/lnd/lnrpc/watchtowerrpc";
+
+service Watchtower {
+        /** lncli: tower info
+        GetInfo returns general information concerning the companion watchtower
+        including it's public key and URIs where the server is currently
+        listening for clients.
+        */
+        rpc GetInfo(GetInfoRequest) returns (GetInfoResponse);
+}
+
+message GetInfoRequest{
+}
+
+message GetInfoResponse {
+        /// The public key of the watchtower.
+        bytes pubkey = 1 [json_name = "pubkey"];
+
+        /// The listening addresses of the watchtower.
+        repeated string listeners = 2 [json_name = "listeners"];
+
+        /// The URIs of the watchtower.
+        repeated string uris = 3 [json_name = "uris" ];
+}