Implement user authentication with JWT, including login and registration features

backend/api/serializers.py

@@ -1,8 +1,42 @@
 # DRF serializers for the backend API will be added here.
+from django.contrib.auth.models import User
+from django.contrib.auth.password_validation import validate_password
+from django.core.exceptions import ValidationError as DjangoValidationError
 from rest_framework import serializers
+from rest_framework_simplejwt.serializers import TokenObtainPairSerializer
 from .models import Template, CheatSheet, PracticeProblem
 
 
+class CustomTokenObtainPairSerializer(TokenObtainPairSerializer):
+    @classmethod
+    def get_token(cls, user):
+        token = super().get_token(user)
+        # Add custom claims
+        token['username'] = user.username
+        return token
+
+
+class UserSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = User
+        fields = ('id', 'username', 'password')
+        extra_kwargs = {'password': {'write_only': True}}
+
+    def validate_password(self, value):
+        try:
+            validate_password(value)
+        except DjangoValidationError as e:
+            raise serializers.ValidationError(list(e.messages))
+        return value
+
+    def create(self, validated_data):
+        user = User.objects.create_user(
+            username=validated_data['username'],
+            password=validated_data['password']
+        )
+        return user
+
+
 class TemplateSerializer(serializers.ModelSerializer):
     class Meta:
         model = Template