Duplicate transactions

[jantman]

I was using the transaction input form from a device with poor connectivity, and ended up with duplicate transactions - specifically, 2 transactions with the same content. This seemed to happen intermittently. E.g.:

2017-05-11 00:17:19,122 [INFO transactions.py:293 - biweeklybudget.flaskapp.views.transactions.submit() ] creating new Transaction: {'description': 'Foo', 'date': datetime.date(2017, 5, 10), 'actual_amount': 92.95, 'account_id': 1, 'budget_id': 14, 'notes': ''}
2017-05-11 00:17:19,137 [INFO db.py:172 - biweeklybudget.db.cleanup_db() ] Closing DB session
2017-05-11 00:17:21,313 [INFO db.py:172 - biweeklybudget.db.cleanup_db() ] Closing DB session
2017-05-11 00:18:08,537 [INFO transactions.py:293 - biweeklybudget.flaskapp.views.transactions.submit() ] creating new Transaction: {'description': 'Kroger', 'date': datetime.date(2017, 5, 10), 'actual_amount': 6.43, 'account_id': 1, 'budget_id': 12, 'notes': ''}
2017-05-11 00:18:08,556 [INFO transactions.py:293 - biweeklybudget.flaskapp.views.transactions.submit() ] creating new Transaction: {'description': 'Kroger', 'date': datetime.date(2017, 5, 10), 'actual_amount': 6.43, 'account_id': 1, 'budget_id': 12, 'notes': ''}
2017-05-11 00:18:08,561 [INFO db.py:172 - biweeklybudget.db.cleanup_db() ] Closing DB session
2017-05-11 00:18:08,570 [INFO db.py:172 - biweeklybudget.db.cleanup_db() ] Closing DB session

I don't have gunicorn logs (#63) but it looks like this is coming from the UI side.

Probably need to enable debugging of any POST requests (or anything else that manipulates data) and then try to reproduce this, maybe by artifically injecting latency, and then figure out how to prevent it in the future. My gut reaction is that high latency is probably causing jquery retries...