Backend: Onboard Patient

create post /patients/add api for onboarding new or existing patients to service
if existingPatient flag is true, then OP number must be available in request and same can be stored to patient entity, if not create new OP number by firstTwoCharOfName + Last4DigitsOfTimeInMilliSec + RandomNumberBw1000And9999
validate details like name, gender, birth date, phone number
check if an entity already exists for op number, if provided
if all checks passed, then store new entity to repo

arun07aj / token-management-service