feat: enable retire dataset function

[tombrooks248]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

Adds a retire mode to the Postgres loader image: task/pgload/retire.py and task/retire.sh count a dataset's rows in entity, old_entity and entity_subdivided and, unless it is a dry run, delete them in one transaction. The Dockerfile's ENTRYPOINT becomes CMD so a caller can run ./retire.sh instead of ./load.sh by passing a command, as the collection task already does. No current caller passes a command (the three Airflow DAGs only set environment variables and the task has no S3 triggers), so loading behaves exactly as before.

Why

Part 2 of digital-land/digital-land-builder#64. Changing a dataset's environment value in the specification stops it being built but leaves its entities in Postgres, so its entity pages and API results stay live. The retire-dataset DAG in airflow-dags will run this mode as its postgres task, keeping the code that removes rows next to the code that loads them. Only DRY_RUN=false deletes anything, matching the collection task's retire mode. Nothing runs this mode until the airflow-dags change is merged.

Related Tickets & Documents

• Ticket Link
• Related Issue #
• Closes #

QA Instructions, Screenshots, Recordings

Built the image from this branch locally and ran it against a throwaway PostGIS database:

• With no command (how the three Airflow loader DAGs call it) the image still runs load.sh: docker inspect shows Entrypoint=null, Cmd=["./load.sh"].
• ./retire.sh with DATASET_NAME=company and DRY_RUN unset, or mistyped as flase, counted the rows (2 entity, 1 old_entity, 0 entity_subdivided) and changed nothing.
• DRY_RUN=false removed only the company rows; the other datasets' rows were untouched. Running it again removed 0 rows and exited 0.

Once merged, dev and staging deploy automatically. Before approving production, run manual-postgres-loader in dev on a small dataset to confirm loading still works.

Added/updated tests?

We encourage you to keep the code coverage percentage at 80% and above. Please refer to the Digital Land Testing Guidance for more information.

• Yes
• No, and this is why: please replace this line with details on why tests
  have not been included
• I need help with writing tests

[optional] Are there any post deployment tasks we need to perform?

[optional] Are there any dependencies on other PRs or Work?