Refactor HTTP handling to add error handling and reduce duplication

[tfmorris]

Fixes #192

• DRY up HTTP handling so that there's only a single place HTTP client headers need to be worried about
• Add error checking so that it doesn't attempt to parse non-JSON responses
• Update WDTK dependency to the version that includes the User Agent fix - this was moved to a separate PR to reenable the CI pipeline and was already merged
• Update to Java 11 to match OpenRefine (and because the code uses Java 11 features like isBlank())

Some non-essential changes which are included, but could be removed (the current code was making my head hurt):

• rename confusingly overloaded method name which has different functionality
• refactor URL building to not depend on state stored in fields

[Copilot]

Pull Request Overview

This PR refactors HTTP handling in the Commons importer to centralize client header management, adds proper error handling for non-JSON responses, and updates dependencies to align with OpenRefine standards.

• Centralizes HTTP handling logic to eliminate code duplication and improve maintainability
• Adds error checking and response validation for API calls
• Updates Java version to 11 and WDTK dependency to stable release

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/main/java/org/openrefine/extensions/commons/importer/FileFetcher.java	Refactors HTTP client usage, adds error handling, and extracts URL building logic
pom.xml	Updates Java version to 11, OpenRefine version to 3.9.5, and WDTK dependency to stable release

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[Abbe98]

Thank you so much Tom! I will get to this soon and make sure to make another prerelease.

I want to update the release documentation before making a proper release, my hope is to get to that next week giving this a few days in the wild.

[Abbe98]

Thank you @tfmorris!