Failed inserting subscriber signup for subscriber id: <long numeric ingenico txn id>: 8002: Found matching recurring contribution(s): <6 digit contribution_recur id>

We are NOT actually losing any data - there already exists a recur record with the invoice ID and token. We just should silently drop the message.

These seem to happen because the check we use at the start of the subscr_signup import looks for an existing subscription whose trxn_id matches the message's subscr_id. The message's subscr_id has the bare gateway_txn_id and the matching recurring contribution has the gateway_txn_id prefixed by 'RECURRING INGENICO'.