Group each filter in repository to avoid precedence issues

[nirolevy]

Overview

This Pull Request fixes a bug related to the handling of multiple $OR conditions in a Filter query.

When multiple $OR conditions were present in a query, they were not being combined correctly during the SQL query construction process, leading to incorrect query results or errors. This fix updates the logic in pycsw/core/repository.py to ensure that a list of logical expressions (filters) is properly combined when constructing the final backend query.

Related Issue / Discussion

Closes #1154

Additional Information

Contributions and Licensing

(as per https://github.com/geopython/pycsw/blob/master/CONTRIBUTING.rst#contributions-and-licensing)

• I'd like to contribute bugfix to pycsw. I confirm that my contributions to pycsw will be compatible with the pycsw license guidelines at the time of contribution.
• I have already previously agreed to the pycsw Contributions and Licensing Guidelines