Handle '@' in username

[ablyes]

handle the case where the username contains one or more '@' char (like an email address used as username).

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[ablyes]

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[plaird]

FYI there are some split_url() tests that have weird urls that this probably won't work for. Not sure if those are real cases somebody has, or not.

https://github.com/bazelbuild/rules_jvm_external/blob/master/tests/unit/coursier_test.bzl#L208

[ablyes]

I think it's not realistic to have a host with @
My commit should fix those 2 cases:
username@whatever.com:password@host
username@whatever.com@itLikes@icanputanotheronehere@:password_with_@_why_not:host

[plaird]

I agree, I don't think having that @ char in the path, in unencoded form, is even legal. But just FYI someone thought it was a valid use case.

[jin]

Could you add tests?

[ablyes]

Yes, I will do that.
May be just delete the none realistic tests also.

[shs96c]

This makes sense. Thank you for the PR!