Add "under discussion" as status

[crowbot]

Feedback from WYPTE:

Because some issues (eg. three carriages on commuter services) are not easily resolvable and can require Government/DfT funding decisions, would it be possible to have a third category such as ‘Under discussion’ rather than them staying as unresolved, which makes them appear that nothing is being done. Perhaps you could review cases in this category or set dates for review/updates.

[fmtdixon]

This would be really helpful because some issues really are "awaiting developments"