Exposure configuration parameters not validated

[michael-burwig]

The exposure configuration parameters are currently not validated after being read from the respective yml file. The validation code in ExposureConfigurationValidator is currently used in tests only.

However, the expected behavior shall be the following:

• The RiskScoreParameters object is constructed based on yml file. (✅)
• ExposureConfigurationValidator performs validation of the parameters.
• In case of a failed validation, do not publish the exposure configuration parameters, but do generate and publish the diagnosis key bundles.
• Clarify whether to keep any previously present (valid) configuration parameters on the object store if a validation error occurs.
• Any validation errors shall be logged appropriately.