Link/Unlink an address to a user account from profile page

[Tbaut]

Partially needs #15

• Front-end: List user accounts/addresses with polkadot-js extension api and let user select an address (see example implementation)
• Front-end: Request a message to sign to Back-end
• Back-end: Generate a message to be signed with random number (stored in DB)
• Front-end: Request the user to sign this message and submit signed message to back end (needs Implement signRaw polkadot-js/extension#196)
• Back-end: Verify the signed message, if valid link the user with the address
• Back-end: Add address array to public endpoint

[erler]

Mocks

No addresses detected

Available addresses

Linked & Available addresses

Hover Styles

Went with the social button styles from posts. lmk if you think they need color / look non-interactive

[Tbaut]

Thanks, I think it looks good, let's see in practice. BTW the Unsubscribe button should have the same behavior than this one I believe.