Merge branch 'hotfix/fonts-with-https'
Added UserApiTestCase to cover user signup (expected) failures
Added UserValidation to prevent user to signup with unallowed caracters #507 #541
Simplified username validation #507 #541
Completed username error message + added front-end validation
Merge branch 'hotfix/login-fix'
Merge tag 'login-fix' into develop

Hotfix signup unvalid username