CSV creator issues

[pmk01]

### Ready
- [x] Filter on field value (When selecting an individual value (eg. Wikipedia), allow to download ONLY those candidates with/out that field entered.)
- [x] Not all fields are in the csv builder - no demographic options, for example.
- [x] gender
- [x] birth_date
- [x] image_url
- [x] favourite_biscuits
- [x] statement_to_voters
- [ ] Ideally It could have a simply dropdown for election type. Or, at any rate, we should explain our ID system on the page.
- [ ] Filter on NUTS
- [ ] Add an uncontested filter
- [ ] Organisation type (county, unitary, etc)

### Later
- [ ] Request: add cancellation reason.

https://candidates.democracyclub.org.uk/data/

~Can't add elected column to csv, can only filter by it.~ ~Ability to filter on cancelled would be appreciated.~

[pmk01]

~I got a 500 when selecting 'all election fields'~

[pmk01]

~Request: add cancellation reason.~

[sjorford]

~The paging buttons don't include the search criteria, so they just go back to paging through the full dataset e.g. https://candidates.democracyclub.org.uk/data/?election_date=&ballot_paper_id=batley&election_id=&party_id= "next" links to https://candidates.democracyclub.org.uk/data/?page=2~

[pmk01]

~Not all fields are in the csv builder - no demographic options, for example.~

[symroe]

I got a 500 when selecting 'all election fields'

@pmk01 Is this still a bug? I can't re-produce it

[pmk01]

Looks like it's fixed now! I can't replicate it anyway.

[pmk01]

Can't get council gss codes out of this, only wards

[pmk01]

Observations from others:

~UX glitch: The “additional fields” checkboxes don’t remain ticked after submission (and the accordion is collapsed, making it non-obvious that they’re not ticked). So when I adjusted the filters and resubmitted, I lost my additional fields.~

~Feature: it would be handy to have a field output that tells me whether it’s a by-election or not (rather than having to export two separate files)~

~a copy of the pagination above the (often long) list of results, as well as a copy of the Download CSV button nearer the top - having to scroll all the way to the bottom for this (the thing you're here for!) is a pain that seems strange.~

[pmk01]

Ideally It could have a simply dropdown for election type. Or, at any rate, we should explain our ID system on the page.

[pmk01]

currently missing gender birth_date image_url favourite_biscuits statement_to_voters

[symroe]

Cancellation reason: I'll keep this on the list, but we don't currently import / store this in YNR so I'll mark it as out of scope for now

[pmk01]

If you select a nation, it auto-filters. But then you select and filter additional fields, and it reverts to 'all'.

[pmk01]

Can get uncontested by filtering elected & cancelled, but this isn't obvious. A single filter would be useful.

[pmk01]

Ability to filter by council type - county, unitary, metropolitan borough, etc - would be very useful