test(ads-client): added additional unit test for staging URL to ensure runtime safety.

[copyrighthero]

Changes

This PR added an additional unit test for the MARS staging URL to catch potential URL issues in the pipeline.

This PR also introduced a new shared component called url-macro that validates the URLs during compile time when devs choose to use the Url crate; investigation finds the repo have three main ways of coding URLs: const &str, Url::parse(), and Lazy<Url>, this utility could potentially help devs who prefer stricter verification before issues reach runtime.

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