normally, we ask user to register before they can do the survey.
when user go to another survey, we ask him to register again.
in our website, we have 15000 surveys.we hope user register once then we can use user profile in all surveys.
now we have a user center,4million username+password data stored in mysql database with md5+salt.
can limesurvey use our user-center as the user profile platform?