* test(billing): Calculate time deltas from a fixed time
Some time calculations are impacted when using the current day vs. the start of the month.
* test(db): Conditionally skip tests at end of month
Certain tests fail when run on the last day of the month because of edge cases in the setup of test data (for example, if today is May 31 and NZ time is June 1). This adds conditional logic to skip those tests when run on the last day of a month.
* CR: typo
These functions will ensure that UTC time is used for billing queries,
eliminating the need for the repository to set the timezone. This also
means the repository no longern needs a writer.