Allow user-controlled encryption keys

[paustint]

Describe the problem you are trying to solve
As an added layer of security, we could consider allowing generating an org decryption key that only the user controls so that org credentials could not be decrypted without that.

Thoughts:

1. allow user to choose "extra encryption"
2. Generate a key for the user - and tell them to store it in their password manager
3. We store the key in their browser so the user only needs to enter it when using a new browser session
4. Upon login, if the orgs are encrypted - ask for the key
5. If the key is unavailable, then the user would be required to generate a new key and re-connect all of their orgs

Benefits:
Org auth tokens stored in Jetstream's DB would not be able to be decrypted with any encryption keys housed within jetstream's infrastructure.