Update Fernet database value encryption to bcrypt

[spwoodcock]

Problem

• We use Python cryptography.Fernet.
• bcrypt on the database level might be better.

Solution

• Enable bcrypt encryption on database for odk_token value.
• Write a migration for converting between Fernet --> bcrypt

Additional context

• This is good security practice, but is low priority, as the odk_token is not a critical problem if compromised.
• We can also refresh the odk_token if it is suspected to be compromised.
• I had already assessed this and decided against it, but feel like it's worth looking into again.