BOF dates inconsistent / absent on concluded groups page

[jennifer-richards]

Describe the issue

While looking at #7350, I noticed that the "concluded" date was blank for many of the current set of concluded BOFs. This is because groups in the "BOFs" section are selected as in the "bof-conc" state but the "concluded" date comes from the ChangeStateGroupEvent that put the group in the "concluded" state.

I think that situations where a "bof-conc" group has a "concluded" state change event will be uncommon, but I might be misunderstanding the group lifecycle.

Edit: this also affects the "start" date, which is similarly looking only at the"active" state. There're also some warts caused by inconsistent data that will need to be cleaned up by a database grooming exercise before we can fully fix this.

Code of Conduct

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[jennifer-richards]

n.b., this ticket is closed because #7771 fixed things as far as accurately showing the date data as they exist in the database. Some of the data themselves, especially for older BOFs, are still in need of grooming. This may require fairly extensive model changes.