[feature] Powermail Backend Template like List.html allow rendering custom Field-Types without Template Overrides

[typoworx-de]

I'm actually struggling with a powermail extension which maybe extends Powermail with a custom Field-Type. So far so good, but Powermail Backend Templates like List.html don't allow adding rendering for such custom fields without overriding the whole Template-File.

I think it would be more reliable to either implement:

• <f:render partial="Module/Types/{typeName}" optional="1" />
• or by implemeting a viewHelper with PSR-Signal being able to render/select a custom Partial to be rendered

Both of these would also solve the issue having multiple extensions trying to override List.html adding custom types on their own.