Crash when voting as anonymous participant using XID only

[brendanarnold]

Steps to recreate

• Create a debate and add some seed statements
• Disable Facebook and Twitter on the debate
• Vote as a user with an XID
• Get a 500 server error

Cause

This sequence hits sql.ts which has some fields defined in participants_extended table which don't exist in the current schema. E.g. permanent_cookie, origin, encrypted_ip_address, encrypted_x_forwarded_for

[brendanarnold]

There is a GDPR concern here as IP addreses appear to be being stored - in practice the encrypted_ip_address field is NULL in our tests but as far as I can tell this isn't used anywhere in the app. This adn the encrypted_x_forwarded_for should be removed as part of this ticket