feat: phone auth tests and fixes

backend/apps/accounts/serializers.py

@@ -25,6 +25,7 @@ class UserSerializer(serializers.ModelSerializer):
 
 class RegisterSerializer(serializers.ModelSerializer):
     password = serializers.CharField(write_only=True, min_length=8)
+    phone_number = serializers.CharField(max_length=20, required=True)
 
     class Meta:
         model = User