Display person consents when merging

[pbanaszkiewicz]

This fixes #2370.

[elichad]

I've discussed the consents merging strategy with Maneesha and Rob, and we've settled on always using the most recent consents. This shouldn't be something the user doing the merge can select. Could you update this PR to:

• remove the choice between A and B and replace it with text such as "Use the most recent consents"
• perhaps show the timestamps for the consents so it's clear which will be used
• program this strategy in the backend. It looks like the "combine" option used to do the same thing, so hopefully some of that code can be used directly

[pbanaszkiewicz]

@elichad sure. I will work on this later this week.

[elichad]

Great, thanks.
Another idea that came out of the discussion was that we could send an email to the merged person, letting them know that their records have been merged and that they should check everything is okay (consents and the rest of their info). I'll make a separate issue for that as I think it fits better into the email automation project.

[pbanaszkiewicz]

This is WIP and may require updated tests.

[pbanaszkiewicz]

@elichad Ready for your re-review.

[elichad]

Looks good to me 👍