Billogram + Plastiq Integration

Keep Billogram and Plastiq aligned: when finance events happen in one, update the other automatically.

Example: when Billogram's "Watch Billograms/Invoices" fires, WEXTL can "Create a Client Secret" in Plastiq. Billogram has 3 triggers (including Watch Billograms/Invoices, Watch Customers, and Watch Items); Plastiq has 26 actions (including Create a Client Secret, Create a Payer, and Create a Payment from a Payment Intent).