Ability for custom connections to build URLs for i.e. Nextcloud Talk and Nextcloud Forms for WIdgets

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Feature request

Which Nextcloud Version are you currently using: 34

Is your feature request related to a problem? Please describe.
I am building a IntraVox site for scientific research teams. They want to have a complete overview over their current activities across their team. This means they also want to have access to most recent talk messages and most recent Nextcloud Forms. However, the custom connection-builder in IntraVox doesn't allow this completely. I've managed to create a widget with the most recent messages, however they all link to the IntraVox main page as a default URL. If i could 'build' URLs it would help me a lot.

Describe the solution you'd like
If i could 'build' URLs more detailed it would help me a lot. I'm currently brewing on a solution I might propose as a PR soon if all goes well.

Describe alternatives you've considered
I've tried doing it using the current custom connection builder. This brings me halfways. Messages are shown but links are wrong (defaulted to the IntraVox main page)

Additional context
I've attached a screenshot of the widget so far. Rendering is great. Links are not good.

Start by inspecting the custom connection builder and the widget link-generation path described in the issue. Reproduce the current behavior with recent Nextcloud Talk messages and Nextcloud Forms, then verify that custom connections can generate their destination URLs instead of defaulting to the IntraVox main page.