Move licence-changes to endpoint and split work

https://eaflood.atlassian.net/browse/WATER-4546

> Part of the work to migrate management of return versions to WRLS from NALD

During the import from NALD, if a licence end date is changed, for example, if it has been revoked in NALD, our return version functionality needs to know about it. This is so we can reissue the return logs for the licence to match the changed end date.

We are actively trying to move away from the legacy code base, so this work was always going to be done in here. Initially, it would be triggered by our [own import process](https://eaflood.atlassian.net/browse/WATER-4535), which was due to replace the legacy one. But that was when we thought ReSP would be taking over from NALD.

Now, the plan is for WRLS to encompass the final abstraction leg and take over from NALD. There is little point in replacing a complex import we intend to switch off in the next year.

But, knowing we'd need something in the interim, we created the [/jobs/licence-changes job](#1593). The intent was to schedule this after the first [NALD import job](https://github.com/DEFRA/water-abstraction-team/blob/main/jobs/import.md#nald-import) had completed (the one that downloads and extracts the NALD data) but before the main [licence import
  job](https://github.com/DEFRA/water-abstraction-team/blob/main/jobs/import.md#licence-import). That way, our job could compare the NALD and WRLS licence records to determine if an end date has changed.

But then we had our 'doh!' moment.

Our reissue return logs engine expects to be given a licence ID and the date the change applies. However, the WRLS licence record needs to have been updated for it to determine the start and end dates of the new return logs.

If we schedule `/jobs/licence-changes` before the licence import job, it will see the change but won't reissue anything because the WRLS record won't have been updated. If we schedule it after, it won't see any difference and won't trigger the reissue.

Doh!

So, we've needed to change tact on this completely. Now, we intend to

- _trigger_ `/licences/end-dates/check` from the [NALD import job](https://github.com/DEFRA/water-abstraction-team/blob/main/jobs/import.md#nald-import) rather than schedule it
- refactor `/jobs/licence-changes` as `/licences/end-dates`, but instead of processing changed licences it [stores the details of the change in a table](DEFRA/water-abstraction-service#2666)
- add a new `/licences/end-dates/process` endpoint that processes these 'licence change' records, and which will be triggered from the [licence import job](https://github.com/DEFRA/water-abstraction-team/blob/main/jobs/import.md#licence-import)

This change handles the refactoring and creating of the endpoints, plus addition of a new model for for the new table.