Feature/callbacks (#2678)

* wip

* initialize callbacks

* wip

* smtp

* list_service_interfaces

* wip

* wip

* fix domains

* fix hostname handling in NetService

* misc fixes

* getInstalledPackages

* misc fixes

* publish v6 lib

* refactor service effects

* fix import

* fix container runtime

* fix tests

* apply suggestions from review

sdk/lib/util/GetSystemSmtp.ts

@@ -15,9 +15,7 @@ export class GetSystemSmtp {
    * Returns the system SMTP credentials. Does nothing if the credentials change
    */
   once() {
-    return this.effects.getSystemSmtp({
-      callback: () => {},
-    })
+    return this.effects.getSystemSmtp({})
   }
   /**
    * Watches the system SMTP credentials. Takes a custom callback function to run whenever the credentials change