Add is_unavailable to DependencySerializer

Add the is_unavailable status to the DependencySerializer. Use
SerializerMethodField and implement a function to fetch the
is_unavailable value from the PackageVersion model.

Implement tests for the endpoint using the serializer. The tests
should verify that the field is present and correctly reflects the
result of the is_unavailable function.

Refs. TS-2276

django/thunderstore/api/cyberstorm/tests/test_package_listing.py

@@ -1,5 +1,6 @@
 from datetime import datetime
 from typing import Optional
+from unittest.mock import Mock, patch
 
 import pytest
 from rest_framework.test import APIClient
@@ -9,11 +10,13 @@
     get_custom_package_listing,
 )
 from thunderstore.community.factories import (
+    Community,
     CommunityFactory,
     PackageCategoryFactory,
     PackageListingFactory,
 )
 from thunderstore.repository.factories import (
+    NamespaceFactory,
     PackageRatingFactory,
     PackageVersionFactory,
     TeamMemberFactory,
@@ -334,3 +337,39 @@ def test_dependency_serializer__when_dependency_is_not_active__censors_icon_and_
 
 def _date_to_z(value: datetime) -> str:
     return value.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize("return_val", [True, False])
+@patch("thunderstore.repository.models.package_version.PackageVersion.is_unavailable")
+def test_package_listing_is_unavailable(
+    is_unavailable_func: Mock,
+    return_val: bool,
+    api_client: APIClient,
+    community: Community,
+) -> None:
+    is_unavailable_func.return_value = return_val
+
+    package = "Mod"
+    target_ns = NamespaceFactory()
+
+    target_dependency = PackageListingFactory(
+        community_=community,
+        package_kwargs={"name": package, "namespace": target_ns},
+    )
+
+    target_package = PackageListingFactory(community_=community)
+    target_package.package.latest.dependencies.set(
+        [target_dependency.package.latest.id],
+    )
+
+    community_id = target_package.community.identifier
+    namespace = target_package.package.namespace.name
+    package_name = target_package.package.name
+
+    url = f"/api/cyberstorm/listing/{community_id}/{namespace}/{package_name}/"
+    response = api_client.get(url)
+    response_dependencies = response.json()["dependencies"][0]
+
+    assert "is_unavailable" in response_dependencies
+    assert response_dependencies["is_unavailable"] == return_val

django/thunderstore/api/cyberstorm/views/package_listing.py

@@ -23,6 +23,7 @@
 from thunderstore.community.models.package_listing import PackageListing
 from thunderstore.repository.models.package import get_package_dependants
 from thunderstore.repository.models.package_version import PackageVersion
+from thunderstore.community.models.community import Community
 
 
 class DependencySerializer(serializers.Serializer):
@@ -44,6 +45,7 @@ class DependencySerializer(serializers.Serializer):
     name = serializers.CharField()
     namespace = serializers.CharField(source="package.namespace.name")
     version_number = serializers.CharField()
+    is_unavailable = serializers.SerializerMethodField()
 
     def get_description(self, obj: PackageVersion) -> str:
         return (
@@ -55,6 +57,13 @@ def get_description(self, obj: PackageVersion) -> str:
     def get_icon_url(self, obj: PackageVersion) -> Optional[str]:
         return obj.icon.url if obj.is_effectively_active else None
 
+    def get_is_unavailable(self, obj: PackageVersion) -> bool:
+        community = Community.objects.filter(
+            identifier=obj.community_identifier
+        ).first()
+
+        return obj.is_unavailable(community)
+
 
 class TeamSerializer(serializers.Serializer):
     """