Increase test coverage to 90%

[jpmckinney]

Testing these 8-10 files would get us there.

[jpmckinney]

Test coverage was being reported as 76%, but this number was being inflated, because tests directories inside the application code were being counted. The real number is currently 59%. (2024: now 70%.)

https://coveralls.io/github/open-contracting/pelican-backend?branch=main

[jpmckinney]

We can mock Pika methods to test the workers.

[jpmckinney]

• consistent.tender_value: Add test fixture for non-number amount

[jpmckinney]

• Convert more of the test files to the new-style tests, using CompiledReleaseTests (and any new helper classes to be created for dataset-level and/or time-based checks).