Avoid duplicate transactions

[AleTopp]

As said in the README this script for each SW transaction creates two FF transactions.
I would suggest that one of them could not be necessary, as in my use case: I upload transactions from bank statement, add description and categorize them; then use this script, so the first transaction created by it would be a duplicate (Card -> Supermarket).

Maybe another env var AVOID_DUPLICATE_TRANSACTIONS could be created, and the script could check (before adding it) that a transaction on the same day and with same amount (and maybe similar description) exists or not, possibly prompting something to the user (maybe this is not desirable), and split that transaction, instead of creating a new one.

I could delete manually the transaction from the bank statement, but it is not what I want, since from the bank there are also other information I want to keep.

If this is something desirable, I would be glad to help on a PR about it.

[adyanth]

We could maybe support a flag to prevent creating the first transaction altogether. Avoiding duplicates by heuristics is bound to be error prone and not something I would like to see with accounting.

So, if that sounds reasonable, or if you had other ideas, happy to hear and accept PRs!

[AleTopp]

I think prevent the creation of the transaction is okay, but in some way we need to split the existing transaction just to categorize correctly on the owed part of the expense.
Maybe heuristic isn't the best way, but I don't see a better way but the manual. So there could be an option to disable the creation altogether, or enable splitting an existing transaction if and only if there is only 1 transaction in FF that corresponds to a (configurable?) heuristic, in other cases it will be prompted in the log to manually enter the split (as it is done now for transactions that have no comment/note).