Add UniqueValidator for slug field of CourseCreateSerializer

api/v1/serializers/course.py

@@ -1,4 +1,5 @@
 from rest_framework import serializers
+from rest_framework.validators import UniqueValidator
 
 from apps.course.models import (
     Category, Course,
@@ -88,7 +89,9 @@ class CourseCreateSerializer(DispatchContentMixin,
                              ):
     title = serializers.CharField(allow_blank=True)
     short_description = serializers.CharField(allow_blank=True)
-    slug = serializers.SlugField(allow_unicode=True, allow_blank=True, allow_null=True, required=False)
+    slug = serializers.SlugField(
+        allow_unicode=True, allow_blank=True, allow_null=True,
+        required=False, validators=[UniqueValidator(queryset=Course.objects.all())])
     content = serializers.ListSerializer(
         child=ContentCreateSerializer(),
         required=False,