Transferring groups does not warn in the same way than transferring projects does

Summary

When transferinga group, the transfer happens directly without confirmation nor warning.

Steps to reproduce

• Transfer a group inside another group

What is the current bug behavior?

There is no confirmation asked

What is the expected correct behavior?

In the same way than with project transfer, I am expecting

• to be warned about the implications and also asked to confim that I really want to do it.
• to receive an email about the projects that were transfered so that I can update my git repositories.

Proposal

The confirmation modal should look like "remove project", and similarly confirm the namespace.