Display username of current logged users

[tchiotludo]

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[ghost]

@tchiotludo: Do you have some preference in the place where we put the username?

[tchiotludo]

The better will be on left menu like the old akhq (and move the login button also here) I think.
The button as somewhat break with big name or in responsive.

If you have some trouble, just remove the button when the user is logged and add a logout button with the current username at the same place

[ghost]

Only added the name in the logout button for now.
Move the button to the sidebar is another challenge