Review reasons to save entity data back to CPRD

### Determine main reasons that data needs to be saved back to CPRD.
## Description:
Saving data from the new entities application back to CPRD is complicated and fairly risky. Up to present, we have assumed that 'all' information must be saved back to CPRD, but we have proceeded without a complete list of downstream processes that directly use this data.

This task is to answer the following questions:
- What downstream processes are run from CPRD, broken down by business type/data point (addr, dirs, etc)?
e.g. Payments? BN Messaging? Gazette? Search?
- Based on the list above, which services can be brought into the new app first to avoid needing to save back to CPRD?

Acceptance / DoD:
- [x] Product Owner advised if task >= 1 full-day, or forms part of the business day
~~- [ ] Requires deployments~~
~~- [ ] Test coverage acceptable~~
- [ ] Peer Reviewed
~~- [ ] Production burn in completed~~