Plugin not working together with @cap-js/attachments plugin

[gecko17]

This plugin is introducing a side effect in the following line:

change-tracking/cds-plugin.js

Line 183 in d537795

const assoc = { ...changes, on: [ ...changes.on, ...keys ] }

The reason is, that you are copying the properties of an object, but not the functions.

The following @sap/cds function is expecting this object to have an .is function, which then causes an error:
line 140 in @sap/cds/lib/core/linked-csn.js

The @cap-js/attachments plugin for instance is invoking this code through this line and hence running into this issue: https://github.com/cap-js/attachments/blob/main/lib/plugin.js#L13

To reproduce the issue:

1. Create a CAP project with both plugins @cap-js/attachments and @cap-js/change-tracking.
2. Make sure that the dependency of the change-tracking plugin is listed after the attachment plugin in the dependencies of the package.json
3. The reason for this is, that both plugins are registering a handler for the compile.to.edmx event and the handlers are executed in the registration order. Only when the change-tracking plugin code runs first, the issue occurs.

Solution would be to create a deep copy of the object.