[Project Flags] Add telemetry to track the values of project-only flags

[MichelleArk]

Housekeeping

• I am a maintainer of dbt-core

Short description

We need to track usage + set values of "project only flags" (those used for gating backwards-incompatible changes) across dbt invocations in order to manage the lifecycle of project flags. For example, determining the impact of switching a default behaviour as well as the prevalence of overrides of the default behaviour.

An alternative approach to make use of our existing deprecation events was also considered. However, these events are only fired during the actual deprecation phase of a flags lifecycle and will not help to inform us on whether it is safe to do so / fully EOL a flag.

Acceptance criteria

• A new under schemas/com.dbt/project_flags/jsonschema/ in the iglu repo - https://www.notion.so/dbtlabs/Tracking-a-new-event-in-dbt-Cloud-344430e7b7e547f4b2b5d3a506e2c2bd?pvs=4

  • This schema should include an unstructured object that represents the key-value pairs for project-only flags for a given invocation of dbt core. This should be unstructured as the project-only flags available will vary across core versions, and because flags may be removed over time as they are fully deprecated.

• A tracking event in core is emitted once the project flags are set.

  • For example, the event could be emitted as part of read_project_flags: https://github.com/dbt-labs/dbt-core/blob/main/core/dbt/config/project.py#L839

Suggested Tests

1. Unit test that asserts the appropriate dbt.tracking method was invoked during read_project_flags

Impact to Other Teams

N/A

Will backports be required?

No

Context

No response

[MichelleArk]

Closing in favor of using our existing deprecation tracking / eventing