Re-rename "ejabberd" service to "xmpp"

Shouldn't matter which implementation is integrated if someone adds
another one

app/models/user.rb

@@ -57,7 +57,7 @@ class User < ApplicationRecord
   end
 
   def devise_after_confirmation
-    enable_service %w[ discourse ejabberd gitea mediawiki ]
+    enable_service %w[ discourse gitea mediawiki xmpp ]
 
     #TODO enable in development when we have easy setup of ejabberd etc.
     return if Rails.env.development?
@@ -137,12 +137,12 @@ class User < ApplicationRecord
 
   def pref_enabled?(key)
     value = preferences.dig(*key.split(":"))
-    [true, "true", 1, "enabled"].include?(value)
+    [true, "true", "enabled", 1].include?(value)
   end
 
   def exchange_xmpp_contact_with_inviter
-    return unless inviter.services_enabled.include?("ejabberd") &&
-                  services_enabled.include?("ejabberd")
+    return unless inviter.services_enabled.include?("xmpp") &&
+                  services_enabled.include?("xmpp")
     XmppExchangeContactsJob.perform_later(inviter, self.cn, self.ou)
   end