Add Validations

[RiflerRick]

@Zaiku1972 there are serializer validations to be added, basically wherever you think there is a possibility of an exception, add a serializer validation
somewhat like...

from rest_framework import serializers
# if validation error is to be raised
raise serializers.ValidationError("msg to be responded with")

note that this is only an example. There are more sophisticated means of raising validation errors