Strict validation hangs with a test case

[prabhu]

We recently noticed that strict validation never completes for urls containing ${ with 3 or more levels in path. Below is an example:

https://github.com/apache/maven-resolver/tree/${project.scm.tag}

It works for below:

https://github.com/apache/${project.scm.tag}
# Takes over 30 seconds
https://github.com/apache/maven-resolver/${project.scm.tag}

[rubensworks]

The regex is probably running into some issues for that case.
We should look into optimizing the regex.
(Definitely open to PRs!)