Improve the code readability

To keep the code more testable and readable, it has to be reviewed and refactored.

For instance, the method https://community.opengroup.org/osdu/platform/domain-data-mgmt-services/rock-and-fluid-sample/rafs-ddms-services/-/blob/main/app/api/routes/data/api.py#L153 take about 100 LOC. It is hard to be tested, reviewed, and read.

Scope:

1. Add the https://pypi.org/project/flake8-functions/ extension for the existing code analyzers (let's start with 70 for CFQ001)
2. Use the cognitive complexity checker (https://github.com/Melevir/flake8-cognitive-complexity )
3. Refactor all Flake8 warnings