Reduce CI test time

[fixlr]

Hi! 👋

I've been lurking on this project for a little while, and happened to have a free morning available when issue #391 showed up in my inbox. 😄

I did some rough benchmarking of db:seed locally, and found that the majority of the time is spent updating talks, and 50%+ of that duration was spent on the following two lines in Talk#update_from_yml_metadata!:

• assign_attributes
• unused_slugs.first

With these two commits, I'm seeing db:seed run in ~27 seconds locally now. 🎉

Before

assign_attributes total elapsed: 46.42051896639168
unused_slugs.first total elapsed: 20.0830240547657

After

assign_attributes total elapsed: 0.23879502154886723
unused_slugs.first total elapsed: 2.2362280655652285

[marcoroth]

Oh sweet, thank you for looking into this @fixlr!

I was suspecting that there were things to improve in the way we seed, but I didn't expect it would be that significant. This is awesome, thank you!

[adrienpoly]

this is great thanks @fixlr