Talks scheduled before the speaker arrives to the conference should show an error

[baldurmen]

While working on the DebConf17 schedule, someone had to go talk by talk and verify manually if the talk was scheduled before the speaker actually arrived to the conference.

I think modifying the custom registration API showcased in #352 to add an "arriving date" and a "departure date" and linking this to the schedule validation would be highly beneficial and time saving.

Maybe having a "confirmed attendance" API (we are using this for DebConf to validate that people will actually be there) would be interesting to validate too?

[stefanor]

Maybe having a "confirmed attendance" API (we are using this for DebConf to validate that people will actually be there) would be interesting to validate too?

I think that'll be resolved in #352, when I get around to finishing that.

[drnlm]

At some point, features start becoming very conference-specific, and it's not sensible to try directly support them in wafer itself. Given that this will require using a custom registration profile, I feel that this is such a feature, and Debconf should be extending the schedule validation logic locally to support this specific request.

wafer should make it easy to extend or otherwise tweak the schedule validation logic, though, so suggestions on how to improve that welcome.

[hodgestar]

Maybe we could add some sort of custom schedule validation hook?