Explain when schemas and database_schemas would be empty within an on-run-end hook

[dbeatty10]

Contributions

• I have read the contribution docs, and understand what's expected of me.

Link to the page on docs.getdbt.com requiring updates

https://docs.getdbt.com/reference/dbt-jinja-functions/on-run-end-context#schemas

What part(s) of the page would you like to see updated?

Add some additional information explaining when the schemas or database_schemas would be empty within an on-run-end hook.

These are some assumptions that would need to be fact-checked before adding them to the documentation:

• in the case of dbt compile, these context variables are empty because dbt hasn't built anything yet [1]
• if a dbt run (or build, seed, snapshot, etc.) doesn't succeed, then these context variables will be empty [2]

Additional information

See dbt-labs/dbt-core#9301 for background context.