Allow transaction filtering by more than one transaction type

[bcm]

We are building a transaction history feature into Copious, and we'd like to show all transactions for an account except holds (which are meaningless to our users). The existing transaction endpoint allows to specify that we want only credits or debits or refunds, but it does not allow us to ask for all three types or to filter out holds. Retrieving all transactions and then filtering out holds on our side is wasteful and anyway is not really practical when "one page at a time" paging (as opposed to the infinite paging strategy that we don't use).

I'd like the transaction endpoint to accept1) a list of transaction types to include and/or 2) a list of transaction types to exclude.

Thoughts?

[matin]

Closed and moving discussion to #14, since that's the core problem. Filtering is supported on any existing field. If there's no field, no filtering.