Admin: feedback missing on form validation

[thimy]

Detailed Description

When editing my own profile for example, saving changes redirects to profile page but we don't get any message about saving.

Context

Users should get a feedback when modifying informations, the page behaviour is the same wether they save or cancel their changes.
We might need to check all form validation.

Possible Implementation

Show a callout on saved change.

[abulte]

Ok on master as of today.