Added:

- ContentSource handling in message
- ContentSource list, add/update ui
- nextPageSelector and imageSelector can be null
- cleanup

src/Entity/ContentSource.php

@@ -62,7 +62,7 @@ class ContentSource
         return $this->NextPageSelector;
     }
 
-    public function setNextPageSelector(string $NextPageSelector): static
+    public function setNextPageSelector(?string $NextPageSelector): static
     {
         $this->NextPageSelector = $NextPageSelector;