accounts: data migration
This MR provides the endpoint that will be used to load all the accounts from old.igem.org to the new server.
This is to be done before merging !186 (merged) so the DB is in consistent state (all users have an account).
A new MR to remove this code (once we have all accounts imported) will be provided later (or together with !186 (merged))
Edited by Fabio Maschi