Creates new user with given email, password and type.
URL : /signup
Method : POST
Header :
"Content-Type": "application/json"
Body :
{
"email": "[valid email]",
"password": "[valid password]",
"type": "[Applicant || Recruiter]"
}
Code : 201 Created
Body :
{
"_id_": "[ID of new user]"
}