Add limitations about CAP Feature toggles to the documentation / readme (#120)

As discussed in [issue
116](#116).

I think it's worth to add this to the readme, as it cost us quite some
time to find this.

---------

Co-authored-by: Frank Hufnagel <[email protected]>
Co-authored-by: Nick Josipovic <[email protected]>
Co-authored-by: Nick Josipovic <[email protected]>

Author: 3 people

README.md

@@ -11,6 +11,13 @@ a [CDS plugin](https://cap.cloud.sap/docs/node.js/cds-plugins#cds-plugin-package
 > 
 > See the changelog for a full list of changes
 
+> [!Warning]
+>
+>Currently, change-tracking is not fully compatible with the [@sap/cds-mtxs](https://www.npmjs.com/package/@sap/cds-mtxs) package which is used to provide extensibility and [CAP Feature Toggles](https://cap.cloud.sap/docs/guides/extensibility/feature-toggles#enable-feature-toggles). 
+>
+>When using multi-tenancy with MTX, the generated facets and associations will not be present in the metadata provided by the service. Therefore, it will not work out of the box. 
+>Until this gap in MTX is closed, we suggest using the `@changelog.disable_assoc` ([see here](#disable-association-to-changes-generation)) for all tracked entities and to add the association and facet manually to the service entity.
+
 
 ### Table of Contents
 
@@ -574,6 +581,7 @@ this.on("UpdateActivationStatus", async (req) =>
 
 The reason is that: Application level services are by design the only place where business logic is enforced. This by extension means, that it also is the only point where e.g. change-tracking would be enabled. The underlying method used to do change tracking is `req.diff` which is responsible to read the necessary before-image from the database, and this method is not available on DB level.
 
+
 ## Contributing
 
 This project is open to feature requests/suggestions, bug reports etc. via [GitHub issues](https://github.com/cap-js/change-tracking/issues). Contribution and feedback are encouraged and always welcome. For more information about how to contribute, the project structure, as well as additional contribution information, see our [Contribution Guidelines](CONTRIBUTING.md).