Refactor ObalkyKnihService: extract query building into separate method

[pavel-patek-mzk]

Description
This PR refactors ObalkyKnihService::getFromService by extracting the query-building logic into a separate protected method.

Why
The goal is to allow overriding only the query construction without duplicating the full getFromService implementation.

Use case
In our case, we need to extend the query with additional parameters (part_no, part_year, part_volume) so that the service can fetch covers for specific periodical/issue instances.

[demiankatz]

Thanks, @pavel-patek-mzk! The refactoring makes sense to me; it just looks like there's a minor style problem in the comments that needs to be adjusted to get the build to pass. I recommend getting in the habit of running composer fix before submitting pull requests, since this automatically corrects many common formatting problems and also will inform you of areas requiring manual attention.

Additionally, I notice that there is currently no unit test coverage for ObalkyKnihService. That's not a requirement to get this improvement merged, but it might be a nice addition to consider for the future.

[pavel-patek-mzk]

Thanks for the feedback! I've applied composer fix to address the style issues. I’ll consider adding unit tests for ObalkyKnihService in a future improvement.

[demiankatz]

Thanks, @pavel-patek-mzk -- tests are passing now, so I will merge this.