Performance Benchmarks

[chrisK00]

I am considering adding a new feature to this year's roadmap that should improve the overall performance of the application by storing the NextPayment date in the database on all writes instead of calculating it every time a subscription is fetched. Completing this issue would then open up an issue for making a PoC that investigates the performance improvments doing the mentioned feature.

Requirements

• Add a new project that makes use of https://github.com/dotnet/BenchmarkDotNet
• We do not want benchmarks inside of unit tests that could potentially fail because of random things. We only want to log the results of the benchmarks. This can maybe be done by exporting the benchmarkdotnet to a json file and logging that result in github actions using a Powershell script that parses the json file and produces an easy to read result
• Add at least one benchmark for SubscriptionsCalculator.GetNextPaymentDate