feat: support loging in with username

[aaqilniz]

This PR enables authentication-jwt to login user with username too.

Checklist

• [x] DCO (Developer Certificate of Origin) signed in all commits
• [ ] npm test passes on your machine
• [ ] New tests added or existing tests modified to cover all changes
• [ ] Code conforms with the style guide
• [ ] API Documentation in code was updated
• [ ] Documentation in /docs/site was updated
• [ ] Affected artifact templates in packages/cli were updated
• [ ] Affected example projects in examples/* were updated

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[coveralls]

Pull Request Test Coverage Report for Build 9421149415

Details

• 6 of 8 (75.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 55.29%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
extensions/authentication-jwt/src/services/user.service.ts	6	8	75.0%
<!--	Total:	6	8	75.0%	-->

Totals
Change from base Build 9419955538:	0.003%
Covered Lines:	9571
Relevant Lines:	12472

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💛 - Coveralls