Remove unneeded aup_accept settings, and make pubsub settings required

Description

In !194 (merged) the AUP_ACCEPTED PubSub topic settings were renamed to USER_UPDATES to better reflect functionality.

This task is to remove the old *AUP_ACCEPTED* settings, and also make these settings required. This will involve removing the USER_UPDATES_PUBSUB_ENABLED setting, and making the other 2 USER_UPDATES* settings required rather than optional. This will be a breaking change, but should be safe to deploy into the current infrastructure.

Further details

Task list

• Remove AUP_ACCEPTED* settings
• Remove USER_UPDATES_PUBSUB_ENABLED setting
• Make other USER_UPDATES* settings required
  • Remove systemchecks that ensure optional settings are valid - effectively covered by making them required.
• Remove unneeded USER_UPDATES_PUBSUB_ENABLED from environment.

Acceptance criteria

• PubSub settings are required and deprecated settings are removed.

Links/references