Measurements endpoint test fix - seeded data for api_source other than "OpenAQ"

It was discovered that if you seed the database with data that has an api_source other than "OpenAQ, there is a 500 response if this data is within range of the parameters, however the tests were asserting that the API would filter accordingly and return the data
Having discussed this with @rstrange-scottlogic, we think this is expected behaviour. There are also sensible logs in docker for the backend-api such as {'type': 'enum', 'loc': ('response', 0, 'api_source'), 'msg': "Input should be 'OpenAQ'", 'input': 'Test', 'ctx': {'expected': "'OpenAQ'"}} to provide more information
Existing test data updated partitioned the data to test this without impacting the other tests
I was not able to test in an automated way that the docker logs are sensible, this is mainly checking for the 500 and preventing the tests from being broken by it

ECMWFCode4Earth / vAirify