[REFACTOR] add swagger auto schema for authentication

apps/custom_auth/views.py

 from rest_framework.authtoken.views import ObtainAuthToken
 from rest_framework.authtoken.models import Token
+from rest_framework.authtoken.serializers import AuthTokenSerializer
 from rest_framework.response import Response
 from rest_framework import status
+from drf_yasg.utils import swagger_auto_schema
 
 
 class CustomAuthToken(ObtainAuthToken):
 
+    @swagger_auto_schema(
+        request_body=AuthTokenSerializer
+    )
     def post(self, request, *args, **kwargs):
         request_data = request.data
         request_data["username"] = request_data["username"].lower()