Automation tests for: 24 create an API to query forecast data

Two test files have been created, one with validation tests, and the other seeding the database and making assertions on the API responses

air-quality-backend/system_tests/api_suite/forecast_api_seeded_data_tests.py
- Wipe and seed the database with 3 test documents
- Parameterised tests with different dates for API params
- test__different_base_times__assert_correct_results_returned
- test__base_time_bva__assert_number_of_results
- test__different_valid_time_from_times__assert_correct_results
- test__valid_time_from_bva__assert_number_of_results
- test__different_valid_time_to_times__assert_correct_results
- test__valid_time_to_bva__assert_number_of_results
- test__results_containing_relevant_base_time
- test__assert_response_keys_and_values_are_correct
air-quality-backend/system_tests/api_suite/forecast_api_validation_tests.py
- validation of optional and required-ness of parameters
air-quality-backend/system_tests/utils/api_utilities.py
- helper methods
air-quality-backend/system_tests/forecast_etl_suite/forecast_calibration_tests.py & air-quality-backend/system_tests/utils/cities_data.py
- folder restructure

ECMWFCode4Earth / vAirify