Old entry trimmer hook.

[umangv]

This hook excludes entries in the import that occurred prior to the last existing balance entry (that is already in the beancount ledger). Since these imported transactions should already be accounted for, the output of bean-extract becomes a lot smaller and easier to read. This is especially useful for financial institutions that do not allow customizing the date range of exported transactions.

By default, we only trim entries already marked duplicate (e.g., by DuplicateDetector). If you do not use DuplicateDetector or want to trim old entries regardless of the "duplicate" metadata, set only_trim_duplicates to False.