Django SaaS Licensing Database Model

Looking for someone who can deliver a database model to manage SaaS Licensing. SaaS licenses are highly volatile as to how they are counted, what their pricing conditions and rental times are. Here's an example License A: - is a product from vendor X - charges per user per month - charges per GB used per month additionally - has a base rate every month - can be cancelled every month, billed monthly - once you have more than 50 active user licenses, your purchasing price goes down by 20% License B: - is a product from vendor Y - charges per machine per month - has a runtime of at least 24 months, billed annually - once you have more than 120 points, purchasing price goes down by 10% Because the underlaying purchasing conditions may change from one month to another, say if for License A you're above 50 active users for a month and then the next you're below again, it would be preferable if purchasing conditions from vendors could be versioned. This is also important as the "base conditions" (how much a license is and after how many users you get a discount) may change every now and then. This is of course crucial for business intelligence and internal cost-tracking. Vendors can have different products; it might even be possible that a vendor charges a base price, regardless of how many licenses are sold. As outlined above, license counters are very different; and people can usually adjust their license amount upwards if needed, so a history of said counters would be preferred. Sometimes licenses are made up off of multiple licenses, license bundles from different vendors. Clients might also have some special pricing conditions for a part of their rental-time. After the licenses run out, they can either be renewed or terminated. Generally, the main idea behind all of this is, not having to create a static set of licenses that exist and can be used, but for users to be able to dynamically create their licenses with the conditions they need. Deliverables Database models in respect to the requirements outlined above. Django models incl. save, receiver methods and querysets. Not using eval().