Clear balanced_customer_href when archiving or closing an account

[Changaco]

Closes #1854.

[chadwhitacre]

I'd feel better about this if we had a better audit trail for financial transactions (#2443). I'm thinking of anti-fraud. If a fraudster closes their account after committing fraud and we lose information about their activity on the site including funding instruments used then that puts us at a disadvantage in responding to the fraud.

[chadwhitacre]

I don't think we want to delete balanced_customer_href here. I do think we want to invalidate all their funding instruments. That would address #1854, and balanced/balanced-dashboard#1353 would enable us to view historical info as needed. But I think we want to keep connection to the relevant Balanced account for debugging purposes.

[chadwhitacre]

IRC

[chadwhitacre]

The archive and close cases are different, though. In the case of a take_over, the user may have balanced_customer_href on the old participant and we should transfer that to the absorbing participant. If there's already a balanced_customer_href on the absorbing participant, we should present them with the option (showing them what identity verifications and funding instruments are associated with each).

[chadwhitacre]

This PR addresses the close case. I think we want to invalidate all funding instruments in the close case, but keep the connection to the Balanced account.

[Changaco]

Closing. IRC.