Release 2022-06-13

Plans can now be created without Options attached to them. This allows business models that don't have any predefined charges but should still be billed according to the billing terms as defined in the Plan. You can create a Plan with billing at the end of every month, then create your contracts, and add products or services to them via additional 'PurchaseItems' which are then billed at the end of each month.
Added a feature that "enforces" the billing of contracts at the start or end of synced billing terms. Currently a contract would first be billed on the contract start date - with the new feature you can "force" it to be created on the first of the month instead. This can reduce the number of invoices your customers receive, as it ensures that all contracts are billed at the first of each month. This does not work if the billing interval has already started. In this case the contract would be billed immediately.
Fixed several bugs