Feature/calibration input validation

[shivkanthb]

Project Robyn

Summary of Changes

This PR introduces a new CalibrationInputValidation class and corresponding unit tests to ensure the validity of calibration input data in the Robyn project. The validation checks include:

• Date range
• Lift values
• Spend values
• Confidence values
• Metric values for each channel in the calibration input
• Objective weights validation

Fixes # (issue number, if applicable)

Type of change

• [x] feat: New feature (non-breaking change which adds functionality)
• [x] test: Additional test coverage

How Has This Been Tested?

A comprehensive suite of unit tests has been implemented to cover various scenarios:

• Valid calibration input
• Invalid date ranges
• Invalid lift values
• Mismatched spend values
• Low confidence values
• Mismatched metric values
• Valid and invalid objective weights

The test_validate function provides an end-to-end test of the validation process

[shivkanthb]

In addition to the calibration validation i also added another function check_obj_weights which seemed important. The function implementation is in place and tested with unit tests but not called anywhere yet in calibration. Feel free to move that later to the right spot (maybe some catch all validation class) or remove if not needed.