Share reconstruction with web3 is particularly long and lacks info

[Tbaut]

How to reproduce:

• login with web3 account

• continue with metamask

• we show the following while metamask should popup:
  

• there's no notion of "the UI is waiting for you to do something". A loader here would be appropriate I think.

• once users signs on Metamask, there's no feedback anymore for 10+ seconds, although there's a lot happening in the background with the share reconstruction. I think we should show a progression bar, eventually with info about what's going on.