Do not hard delete access and access tokens in auth service

[mkurapov]

Context

Original slack thread

Currently in testnet, there is a grants page that shows all of the grants for the user. However, once a user revokes a particular grant (outgoing payment grant), because the grant access is hard deleted from the DB, there is no way to get the grant to match user's wallet addresses anymore. This means in rafiki.money/testnet this grant becomes not visible.

We should not hard delete access when a grant is revoked.
We also hard delete access tokens when a grant is revoked, but for an audit trail, we should soft delete those instead.

Todo

• Do not hard delete access when a grant is revoked
• Soft delete accessTokens when a grant is revoked

[mkurapov]

@njlie

Based on the Slack message, we wanted to soft delete access. Since it doesn't have any status information/expiry or anything on the access model, I think we just don't do anything to it other than removing the delete call when a grant is revoked.