Add analytics event for extract column in chill mode

[romeovs]

Closes #41773

Description

Adds an analytics event that fires when the custom column is created from the table mode via Extract button in the column header

[replay-io]

Status	Complete ↗︎
Commit	e9df66b
Results	⚠️ 6 Flaky ✅ 2447 Passed

[ranquild]

structEvents are deprecated google analytics events that should not be used. Please use snowplow events.

[romeovs]

This is a bit fragile: when we add more extractions, we need to add the expressions used here too.

But AFAIC there is no easy way to get the expressions introduced by an extraction from the extraction itself.

[ranquild]

We could make ColumnExtractionInfo.tag to be a enum and not just a string. We could also define a mapping type used here in a way to make it fail if there is a new tag that is not supported here. Like:

Record<ColumnExtractionTag, string>

Another way could to be to make analytic events match the expression tag either by updating the tag or the analytics spec.

[romeovs]

Ok I've done exactly that, please have another look.

[ranquild]

Inline comments.

[ranquild]

@romeovs same as #42095 (comment)

[romeovs]

@ranquild please have another look, Braden added a helper so we could actually get the extractions from the drill.

That is used to get the functions from the expression generated by the extraction correctly.

[ranquild]

if (typeof arg === "object") walk(...)` without the first if

[romeovs]

Hmm there are some type errors when I try that (because arg can be an opaque object. Is there a case my code is missing?

[ranquild]

metabase/frontend/src/metabase-lib/filter.ts

Line 570 in 4b71e9a

function isExpression(arg: unknown): arg is ExpressionParts {

[ranquild]

because typeof null === "object"

[ranquild]

feel free to move this utility to a different place (expression.ts?)