DUO release leftovers

Continuation from #2314

These items need to be covered before DUO feature can be released:

- [ ] Update Manual (and changelog mention)
- [ ] Write up ADR on DUO, see [rems/docs/architecture](https://github.com/CSCfi/rems/tree/master/docs/architecture) #2848
- [ ] Implement browser tests to cover primary user stories
- [x] #2997
- [ ] perhaps approver-bot / rejecter-bot need to support DUO fields
- [ ] Probably we should add DUO codes 6 and 42
- [ ] Logic should maybe use hierarchy 1 > 42 > 6 > 7 (see DUO hierarchy)

These items are nice-to-haves:

- [ ] Refactor DUO code restriction `:type` - currently restriction type is used to access both restriction field type (e.g. date field or number input or basic input) and restriction translation, but for example `publication moratorium` uses restriction type `:date` which is generic field type
- [x] Do not show DUO codes in application if no resources require DUO codes #3048