[Feature] SSO/discourse account linking

[gimmeliina]

Now we have moved from discord to discourse, it would be nice that we have two way linking into accounts.
Now there is no easy way to contact user from stashdb.

There is several approaches;

• Link accounts via openid and support SSO, and show user link in that way
• add discourse username section to stashdb profile (requires user to manually add account)

Considerations:
Other stash-box instances