Allow basic auth in url.
Improve regex. Add tests.
bug #11601 [Validator] Allow basic auth in url when using UrlValidator. (blaugueux)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #11601).

Discussion
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[Validator] Allow basic auth in url when using UrlValidator.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |
Now an url with basic auth like ```http://username:password@symfony.com``` can be valid.

Commits
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f1ea987 Allow basic auth in url. Improve regex. Add tests.