[DCV-3797] Add Airflow metadata database cleanup how-to

[gams87]

Summary

Adds a customer how-to for cleaning up the Airflow metadata database using the new @task.datacoves_airflow_db_cleanup decorator (Airflow 3 only), covering which tables are cleaned, the decorator parameters, an example DAG, and the recommended dry-run first.

Companion to the code PR datacoves/datacoves#1520.

🤖 Generated with Claude Code

[noel]

@alejandro-datacoves why the new decorator vs just putting the info like astronomer and letting them do it?

Then it could work in airlfow 2 and many ppl would not be moving to airflow 3 any time soon.

I think we shouldnt give ppl things like a decorator that can delete things. I am just thinking we give them a sample dag

[noel]

see comment

[gams87]

@noel

Let's say that with the decorator it would be like batteries included, but we can extract the logic from the decorator and that would be the example DAG.

This is for Airflow 3; I thought it would be a good incentive to migrate to Airflow 3. For Airflow 2 the implementation would be different, but it can still be done.

[noel]

the people who have this problem will be on 2 for a while. so I would at least show both options