PruneDb removes completed jobs (and related runs and errors) from the database if their `lastUpdateTime` is more than `keepAfterCompletion` in the past.

PostgresExecutorRepository is an implementation of ExecutorRepository that stores its state in postgres.

PostgresJobRepository is an implementation of JobRepository that stores its state in postgres.

ExecutorRepository is an interface to be implemented by structs which provide executor information.

JobRepository is an interface to be implemented by structs which provide job and run information.