chore(plugin-server): add property for anonymized created_at

[bretthoerner]

Problem

Some customers really don't want accurate timestamps in their data, and these created_at ones were totally out of their control.

Changes

Add $truncate_created_at property which truncates to the day.

I'm actually not in love with adding this based on a single customer request. Magical properties easily become long-term maintenance burdens. Should the customer write a plugin for this, and then we check for a created_at field on the event instead of hardcoding now()?

Is it safe to give users control over that field? I actually don't know if there is product fallout from "breaking" created_at, I'm assuming it's just a debug column... but if it's a debug column for us, then giving them control will make it very confusing.

Does this work well for both Cloud and self-hosted?

Yes.

How did you test this code?

Unit test.

[bretthoerner]

@tiina303 Curious for your thoughts, related to Zendesk 11991

[bretthoerner]

I changed it to truncate and it feels way less ugly now.

Now my main question is:

1. Should it really just be $truncate_timestamps and apply to the timestamp field, too? (They do this themselves currently, but it feels like anyone who wants this feature would want it for all datetimes)
2. Still unsure if it should be a magical property or become a full plugin type thing. Magical property feels a little less ugly if we think other people will actually use this.

[bretthoerner]

Have plans to hide these from the UI instead.