"Add message": Allow custom communication type

[mal-tee]

in the "add message" modal of /my-requests/ we currently only support the three hard coded communication types. But sometimes companies communicate via internal messages, e.g. DMs or messaging systems behind a login. To track those accurately we should support custom values.

[baltpeter]

I happened to just touch the code related to this, so I thought a bit about this.

Do you think we really need to allow custom values or wouldn't it be enough to add a new value for the case you're describing?

The modal is using the same TransportMediumChooser that is also used in the generators. Adding support for custom values would be really annoying. Tbh, even just adding another static value wouldn't be fun. It would however be really easy to add the new "web form" transport medium there.

What do you think? That certainly wouldn't be perfect but otherwise someone else will have to implement this. :D