Document the where property of generic tests

[shippy]

Description & motivation

This PR describes the where property of generic tests in an FAQ on the main "Tests" docs page. I'm adding it because I've found the property very useful, but information about it has been hard to find.

Pre-release docs

Is this change related to an unreleased version of dbt?

• Yes: please
  • update the base branch to next
  • add Changelog components: <Changelog>[New/Changed] in v0.x.0</Changelog>
  • add links to the "New and changed documentation" section of the latest Migration Guide
• No: please ensure the base branch is current
• Unsure: we'll let you know!

[runleonarun]

Thank you for opening this PR, @shippy (love this username!) We will review this content as soon as we can.

[shippy]

Ha, actually tried the suggested where example with dateadd (previously I stuck to where: "received_at <= '{{ modules.datetime.date.today() - modules.datetime.timedelta(days=1) }}'") and it turns out it's database-specific, i.e. dateadd doesn't work on Postgres. A database-agnostic solution like dbt_utils.dateadd is (1) not a good fit for core docs and (2) I can't actually make it work in a YAML file, so I'll come up with a different example.

[runleonarun]

I wonder if @jtcohen6 has any thoughts on this.

[jtcohen6]

Unfortunately, test configs (including where) don't support macros in their parsing/compilation context today (dbt-labs/dbt-core#4103), so it isn't possible to use dbt_utils.dateadd.

IMO explicitly mentioning that the example uses PostgreSQL syntax would be okay

[shippy]

Added a comment stating the dateadd syntax is Snowflake-specific. (Going off of this blogpost.)

[shippy]

Note to self that maybe this should link the current where documentation, which I found by accident the other day.

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[shippy]

I looked at some other FAQs that linked resource configs and modeled the link on them, but I haven't actually built the docs site locally, so I don't know if it works correctly.

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[runleonarun]

We appreciate your contributions to the dbt product documentation! Unfortunately, we are closing this PR as outdated with merge conflicts. We don't have permissions to edit this fork to fix the merge conflicts so we cannot update this content for publishing.

Feel free to open a new PR if you want to add this content to the docs! 🙇🏻