prosody: ship a proof-of-concept hello world module

hosts/by-name/servo/services/prosody/default.nix

@@ -222,6 +222,8 @@ in
     # - vcard_legacy
     # - version
 
+    extraPluginPaths = [ ./modules ];
+
     extraModules = [
       # admin_shell: allows `prosodyctl shell` to work
       # see: <https://prosody.im/doc/modules/mod_admin_shell>
@@ -237,6 +239,7 @@ in
       # legacy coturn integration
       # see: <https://modules.prosody.im/mod_turncredentials.html>
       # "turncredentials"
+      "sane_hello"
     ] ++ lib.optionals enableDebug [
       "stanza_debug"  #< logs EVERY stanza as debug: <https://prosody.im/doc/modules/mod_stanza_debug>
     ];

hosts/by-name/servo/services/prosody/modules/mod_sane_hello.lua

@@ -0,0 +1,4 @@
+-- simple proof-of-concept Prosody module
+-- module development guide: <https://prosody.im/doc/developers/modules>
+-- module API docs: <https://prosody.im/doc/developers/moduleapi>
+module:log("info", "Hello world!");