Customize Path and title of the Messages box

Problem/Motivation

It is not possible to customize the path and title of the Message Box page. It is set to "/private-messages" by default and cannot be changed.

To my concern, it would be interesting to be able to put this page in a subdirectory like /messages/thread. This would allow to put the messages list block on the /messages page.
The breadcrumbs would therefore be logical:
- List of messages in inbox: Home > Messages
- Discussion details: Home > Messages > Discussion

Proposed resolution

Let set path and title of the /private-messages page in the admin.