Improve profile handling/menu

[kelson42]

Current profile/login UI is always displayed on the top right corner and looks like this:

The current approach works properly but:

• Is a bit unsual display
• Will become maybe a bit unclear when we will support many sources of identities, see https://github.com/openzim/wp1/issues/983

I propose to offer a better approach by:

• Just displaying the usual icon in place

with a hint like "kelson@wikimedia" so we are clear about the identity

• Having a popup menu appearing when clicking on it
• at the end of the popup menu the "logout" menu
• In the midle of the popu menu entry to edit the identity and link directly to the provider of the identity
• I would like here - as well - to make the identity clear by displaying the name "kelson@wikimedia", so there is not ambiguity
• Ideal would be a menu entry to switch the identities very easily

This could/should be pretty standard IMHO for all our platform, so should not be developed specifically for WP1 IMHO.

[kelson42]

@elfkuzco @benoit74 @rgaudin Pinging you just for your information as I want to put in emphasis that SSO client implementation and related stuff should AFAP only done once in Pythong/Vue.