Fix Matrix SIGPIPE and RTL v0.15.8 config schema regressions

- modules/synapse.nix: replace tr|head pipeline (causes SIGPIPE under
  set -euo pipefail) with pwgen -sA0 20 1 which is already in PATH
- modules/bitcoin/rtl.nix: lowercase Authentication->authentication and
  Settings->settings per RTL v0.15.8 schema; add lnServerUrl pointing
  to LND REST endpoint; move swapServerUrl/boltzServerUrl inside
  settings; apply same fixes to CLN branch

Co-authored-by: naturallaw777 <99053422+naturallaw777@users.noreply.github.com>

modules/bitcoin/rtl.nix

@@ -101,33 +101,33 @@ let
       index = 1;
       lnNode = "lnd";
       lnImplementation = "LND";
-      Authentication = {
+      authentication = {
         macaroonPath = "${cfg.dataDir}/macaroons";
         swapMacaroonPath = if cfg.nodes.lnd.loop then "${cfg.dataDir}/loop-macaroons" else "";
         boltzMacaroonPath = "";
       };
-      Settings = {
+      settings = {
         userPersona = "OPERATOR";
         themeMode = if cfg.nightTheme then "NIGHT" else "DAY";
         themeColor = "PURPLE";
         channelBackupPath = "${cfg.dataDir}/backup";
         logLevel = "INFO";
+        lnServerUrl = "https://${lnd.restAddress}:${toString lnd.restPort}";
+        swapServerUrl = if cfg.nodes.lnd.loop then "https://127.0.0.1:8081" else "";
+        boltzServerUrl = "";
         fiatConversion = cfg.extraCurrency != null;
         unannouncedChannels = true;
       } // optionalAttrs (cfg.extraCurrency != null) {
         currencyUnit = cfg.extraCurrency;
       };
-    } // optionalAttrs cfg.nodes.lnd.loop {
-      swapServerUrl = "https://localhost:8081";
-      boltzServerUrl = "";
     }) ++ optional cfg.nodes.clightning.enable {
       index = 2;
       lnNode = "clightning";
       lnImplementation = "CLN";
-      Authentication = {
+      authentication = {
         runePath = runePath;
       };
-      Settings = {
+      settings = {
         userPersona = "OPERATOR";
         themeMode = if cfg.nightTheme then "NIGHT" else "DAY";
         themeColor = "PURPLE";

modules/synapse.nix

@@ -237,7 +237,7 @@ CREDS
       # idempotent without exposing this service credential in the Hub UI.
       HUB_ADMIN_CREDS="/var/lib/secrets/matrix-hub-admin"
       if [ ! -s "$HUB_ADMIN_CREDS" ]; then
-        HUB_ADMIN_USER="sovran-hub-$(tr -dc 'a-z0-9' < /dev/urandom | head -c 20)"
+        HUB_ADMIN_USER="sovran-hub-$(pwgen -sA0 20 1)"
         HUB_ADMIN_PASS=$(pwgen -s 32 1)
         if register_new_matrix_user -c /run/matrix-synapse/runtime-config.yaml \
           -u "$HUB_ADMIN_USER" -p "$HUB_ADMIN_PASS" -a http://localhost:8008; then