[postgres_persistence] Remove param on_flush.

[aelkheir]

Removes parameter PostgresPersistence.on_flush since it has no effect. (reference)

[Bibo-Joshi]

Hi. Sorry for getting back late on this PR.
Looking at the changes, I think that there actually is a misunderstanding: Yes persistence.update_*_data is called depending on the update_interval parameter. However, the parameter on_flush specifies whether each of those calls also automatically writes to database or only keeps the data in memory. if on_flush=True, writing to DB happens only on shutdown, when the Application explicitly calls flush.

[aelkheir]

Hi! not a problem ^^

if on_flush=True, writing to DB happens only on shutdown, when the Application explicitly calls flush

ooh, that does clarify it. I guess I was confused b/c I didn't know when was flush called internally and assumed it should happen after callback had finished. I also now see its mentioned in PostgresPersistence.flush docstring.

I'll be closing. Thanks for the clarification