Fixed URL formatting issue

[ekonopliov]

That was super annoying when forgetting that only URL without "/" ending is acceptable. Now it can work with both.

[omandryk]

Thank you, @ekonopliov, for contributing this fix and for your patience while the project was inactive.

I reproduced the double-slash behavior on the revived master, preserved your original commit and authorship, and integrated it with focused regression coverage in #59. The full Java 8/11/17/21 CI matrix passes on the merged result.

Closing this original PR as completed via #59.