migration: add concern raised by @jan

architecture-docs/data-model-requirements.md

@@ -43,6 +43,8 @@ FooUniversity (Operator)
            * may need to rewrite URLs to blobs automatically, depending on the underlying URL scheme, which may be per setup or application
         * limits? per application? per user? where are these used/set/enforced?
         * TODO: what does e.g. borgmatic need to back up?
+          * complications: in case details such as connections change, those may need adjusting, implying application-specification reconfiguring
+            * potentially propagate thru by e.g. TF?
         * out of scope?: focus on actual state, disregarding reconstructable stuff
 <!-- * application specifics -->
   * pixelfed