add SOPN names to inline membership form

[chris48s]

This PR allows us to edit the SOPN names fields on the inline membership form
These forms are only available if the ballot has a SOPN

The other thing we said we wanted was a way to identify records that don't have the SOPN names set. I started off thinking I would need to implement a custom filter for this. Then after I did it, I realised that we actually kind of get this out of the box. If you add any custom fields to the builder, you automatically get boolean filters for them. So for example:

I think I'm fine with just leaving it there tbh. That said, if we want a combined filter for both fields I still have the code I wrote to hand.

[chris48s]

if we do want a custom filter, this is what I did before realising we probably don't need it 7bab12b
but that commit is not on this branch

[symroe]

This code seems fine but I have two questions:

1. Is the inline membership form the right place for this? It makes that form longer, but maybe that's ok? I think I'd assumed it would be on the name change form at /person/<id>/other-names. In ether case, I think we need to link to the SOPN we're talking about
2. Are we sure we want to require unlocking and re-locking to edit these names? I think most of the edits will be after the ballot is locked, but we don't want to force re-locking for every edit

I think we need to answer 1 before working on 2. @pmk01 I'd like your reckons on this too please

[chris48s]

I'll wait for Peter to chime in before doing anything more on the editing UI.

Did you have any thoughts on the filters? Shall we just roll with the defaults like I have suggested? That will be the same whatever we do on the edit side.

[symroe]

Yeah, I think the current filters are fine for the data export. We might want a way to filter candidates in the front end, e.g to allow people to go through and edit people with missing names. I think we should punt that to a new PR as it also needs a little chat about how to make it useful.

[chris48s]

Here's another thing to think about, which I think is relevant here:

Currently there are some things that are an attribute of a Person, but they should really be attributes of a Candidacy. The most obvious one is candidate statement.

If you imagine a world where we have moved to storing statement as an attribute of a Candidacy, I think what we would actually want is the ability to edit a candidacy (i.e: Joe Bloggs standing in ballot local.adur.mash-barn.2026-05-07) as a stand-alone object. At this point it will have outgrown an inline form on the person.

In that world, I think I would squarely think of "name exactly as it appears on the SOPN" as something that squarely goes in the "edit candidacy" form rather than the "edit person names" form.

Obviously that is kind of a hypothetical, but I reckon it is worth bearing that in mind as a direction of travel.