User LogIn implementation

[kelumsampath]

need to implement following :

1. email and password get by post request body
2. check if there existing user for that email, if not send invalid user response
3. retrieve user password from db , decryption and compare it. if not match send invalid user response
4. generate token for user and send with success response

every response type should as follow :
{status:true/false (required) ,massage:"" (required) ,data:{} (optional) }
status true if process successfully done.