Improving tag selection

[wes-otf]

Currently when adding tags to an application, the dialog can be a little confusing based on the tag hierarchy options.

Issues:

• If a tag has a child, it will show as disabled in the list when there are use cases for the parent being selected
• A group of child tags will be split in the selector depending on if they themselves have children
• It would be nice to show tags in a hierarchical manner like wagtail does

Wagtail tag config

Tag selection prompt

The last outlined issue might be a stretch with how choices work, but I think it could even be better to just have the choices be regular options w/o separators with some small text that shows the hierarchy - ie. something similar to the following in option text:

_{Test Root → Test Child}
Test Grandchild

[frjo]

That e.g "Test Grandchild" is disabled is due to custom Hypha overrides. We can remove them and fallback on the default. Do not remember why this was put in place and #972 does not explain it.