Ability to connect blockstack id to existing local user

[odinho]

It would be nice to be able to add Blockstack ID to a normal user account on the forum.

Issue for tracking. I have no idea if it's possible currently. From forum question.

[odinho]

For the included social logins this seem to work at least. Whether it'll work for a plugin, and even how to do it is unclear to me atm.

• Since the launch of Discourse in 2013, you’ve always been able to add any login method that maps to the exact same email address.

https://meta.discourse.org/t/social-login-issue/58593/12