track deprecations

[beckjake]

Describe the feature

Currently, dbt tracks anonymized information about a few metrics on dbt runs (package installs, invocations, running models, ...). It would be nice to add tracking around deprecation warnings triggering.

As a dbt developer, I'd like to know how many people are using deprecated behavior so we can inform our decision making on when to remove it.

Describe alternatives you've considered

Right now we guess about it.

Who will this benefit?

Anyone making product/feature decisions.

[jtcohen6]

I agree this is valuable, especially as we look to make good on deprecating some long-overdue things.

I think there are two viable Snowplow implementations:

1. Structured event, one per distinct deprecation:
   category: 'dbt'
   action: 'deprecation'
   label: [named deprecation, per this list]

2. Unstructured event, fired once per invocation, containing all active_deprecations as an array. We can flatten it in the database. I think that would require a new custom context, though.

I lean toward the latter, though I know it's more setup. @drewbanin Do you have a preference either way?

[drewbanin]

yep - let's do it. I'd like to make an unstructured event with a single field in it's schema for the deprecation name. I think this is a more sustainable long-term approach than using a bunch of untyped structured events. If there are multiple deprecation warnings in a run, we should just fire one event per deprecation IMO!