`GET /partitionings?partitioning=serializedPartitioning`

[salamonpavel]

Feature

Implement GET endpoint for retrieval of partitionings
GET /partitionings?partitioning=serializedPartitioning
Returns the actual partitioning or 404 if not found in DB.

[github-actions]

Release notes:

• Introduces GET endpoint for partitioning based on partitioning query parameter
• Fixes bug in getPartitioningById method in PartitioningRepository