Add API tests for Rijksmuseum collection endpoint

[helingunderci]

This PR adds automated Rest-Assured tests for the Rijksmuseum API collection endpoint. It includes:

• Basic response validation (status code and JSON format)
• Language-specific content check via culture and base URL segments
• Pagination test using ps parameter
• Sorting test using s=relevance
• Filtering by involved maker (e.g. Rembrandt van Rijn)
• Facet type presence and non-empty validation

All tests are written with JUnit and follow clear structure for future maintainability.