Calculating quota for actual period of performance

[ccostino]

As a part of our efforts to solidify pricing for Notify.gov, we need to make sure the application is able to properly support our partner agreements for accurate billing and cost estimation. This includes making sure we're properly tracking the period of performance, which is the length of time of an agreement (usually 1 year). An agreement can be signed at any time, so we need to make sure we're able to handle arbitrary periods of performance and that billing and account access is properly accounted for.

For the backend

• Add/update an agreement model to capture information related to an agreement, including whether or not the agreement is active and the period of performance
• Create an agreement history model to keep track of old agreements
• For our service model, add a property that references an agreement and the agreement history to track the current past agreements for the service/partner

For the frontend

• Create a way to display the current active agreement information and agreement history

[ccostino]

@stvnrlly I think we have some existing issues around this, correct? Please feel free to add or adjust as necessary!