minor improvements

- README: add matrix room

- examples/configuration.nix: explain why bitcoind is enabled by default

- btcpayserver: group lnd service settings

- clightning:
  Use public onion port only when the onion service is public

  This allows users to enable the onion service while announcing a
  non-onion public address.

- netns-isolation: move `readOnly` attr to the top

- tests: use mkDefault to allow for easier overriding

- tests/btcpayserver: test web server response

modules/netns-isolation.nix

@@ -43,14 +43,14 @@ let
     };
 
     netns = mkOption {
-      default = netns;
       readOnly = true;
+      default = netns;
       description = "Exposes netns parameters.";
     };
 
     bridgeIp = mkOption {
-      default = bridgeIp;
       readOnly = true;
+      default = bridgeIp;
       description = "IP of the netns bridge interface.";
     };
   };