Improve dynamic content loading

[jeriox]

We currently have several points where we dynamically load/send content from JS:

• Consequence approval
• shift edit form: loading form to configure structure and flow
• dynamic formsets.

They all use different approaches and are sometimes a bit cumbersome and brittle. We'd like to improve this, probably by introducing HTMX or using vuejs which is already present in the project. This needs exploration as to what is the best solution.