Add tests for Julia metadata handling

[snoopuppy582]

Summary

Adds JuliaData unit coverage for URL parsing, serialized metadata, JuliaHub URL probing, General registry lookup, download statistics, and update_json orchestration.

Fixes #1106.

Details and comments

The tests mock network calls so they do not depend on JuliaHub, JuliaPackages, the General registry, or Julia download-stat endpoints being reachable during test runs.

Local coverage for ecosystem/julia.py increases to 91% with the new focused tests.

Tests run:

• uv run --python 3.13 ... pytest tests/models/test_julia.py -q
• uv run --python 3.13 ... pytest tests/models -q
• uv run --python 3.13 ... coverage run --source=ecosystem.julia -m unittest tests.models.test_julia && coverage report -m
• uv run --python 3.13 --with black[jupyter]~=26.3 black --check tests/models/test_julia.py
• uv run --python 3.13 ... pylint -rn tests/models/test_julia.py
• git diff --check

[CLAassistant]

All committers have signed the CLA.

[snoopuppy582]

good

[1ucian0]

Thanks!

Tests should mock network interactions, so they do not fail on network issues. Have a look to #1138 as an example.

[snoopuppy582]

Thanks for the review. I tightened the Julia metadata tests so every ecosystem.julia.request_json call now goes through a strict URL-to-payload mock. If the code tries any unexpected URL, the test raises an assertion instead of silently returning a fallback value. The tests also assert the exact mocked request sequence for the JuliaHub, registry, download stats, and GitHub tree probes.

Verified locally:

• python -m unittest tests.models.test_julia -v
• python -m black --check tests/models/test_julia.py
• python -m pylint -rn tests/models/test_julia.py