Duplicate users in DB

[TenDRILLL]

Some users are displayed multiple times on the Database, this seems to be due to users being able to register their account with multiple Discord accounts.

Should check if Destiny user is already registered pre-registration.

[TenDRILLL]

Proposed fix:
if registering and bungie id exists in DB alr,
remove all Argos related roles from old Discord ID and
replace old Discord ID with new Discord ID

We don't need to account for any impersonation cases,
as bungie id is provided via the API oAuth and is spoof-proof.

[Ugi0]

d710cdb should address this
2268bcd and a76715e are also fixes for this solution. Should be tested