feat(data-management): add custom events list

[mariusandra]

Problem

I'm trying to remove the last references to the "load all data"-powered eventDefinitionsModel.

We have a dropdown for custom events under insights/paths, which uses this model. I want to convert it to a regular paginated taxonomic filter dropdown.

The shortest amount of changes to get this working is to split the event_type used by the event_definitions API endpoint to contain two new sub-types:

export enum CombinedEventType {
    All = 'all',
    ActionEvent = 'action_event',
    Event = 'event',
    EventCustom = 'event_custom', // new
    EventPostHog = 'event_posthog', // new
}

As a side effect, we can now add these two items under data management event list as well:

Changes

• Adds two new evert types for event definitions: event_posthog and event_custom, which take all events and either keep or remove those that start with a dollar $.
• Adds the two new types to the filter on the data management page (do we want this? how to call them?)
• Makes the custom elements list in the user paths filter use the new endpoint, instead of the model

How did you test this code?

Wrote tests for the two new filters in the API.

[mariusandra]

If it helps, I'm also happy to hide the UI changes (two new filter options) and split them to a different PR to get the backend stuff merged quicker.

[alexkim205]

nit: the key name sounds pretty specific. Thoughts on calling this is_posthog_event?

[alexkim205]

If its not too much work, it'd be nice to use a divider or indent these sub types since these extra entries could be confusing. Otherwise +1 to hiding this in the UX for this PR and adding in a smaller future one

[clarkus]

Looks like a good change. I think the event option labels would be easier to use if we changed the format of a few. I drew a quick update. Have we flagged these changes for documentation? I can see how users might need more explanation on what each type represents.

What about the other event classifications we've used - specifically verified and raw events. Should those be available here? @alexkim205 thoughts on those other event types?

https://www.figma.com/file/rnaKSVMfWTcpX4cmDbvWsi/Data-Management-%26-Live-Events?node-id=4%3A18853

[mariusandra]

Thanks @alexkim205 and @clarkus ! I'll split the frontend/product work into a separate PR for another round of feedback, and merge in the ✅ 'd backend changes to unblock #11467

going to move this to a separate PR