Fix #180: Letsencrypt import not working

Letsencrypt certificate import procedure was not working on server that had never installed Prosody.
Adding `prosody_user` in the Prosody configuration file to fix this.
Updating the procedure: the `chown` is no more needed in `/etc/letsencrypt/renewal-hooks/deploy/prosody.sh`.

server/lib/prosody/config/content.ts

@@ -1,5 +1,6 @@
 import type { ProsodyFilePaths } from './paths'
 import type { ExternalComponent } from './components'
+import { userInfo } from 'os'
 
 type ConfigEntryValue = boolean | number | string | ConfigEntryValue[]
 
@@ -154,6 +155,8 @@ class ProsodyConfigContent {
     this.global.set('allow_registration', false)
     this.global.set('admins', [])
 
+    this.global.set('prosody_user', userInfo().username)
+
     this.global.set('pidfile', this.paths.pid)
     this.global.set('plugin_paths', [this.paths.modules])
     this.global.set('data_path', this.paths.data)