Resort to fallback URL when package can't be found

Sources/App/Controllers/API/API+PackageController+GetRoute.swift

@@ -90,8 +90,8 @@ extension API.PackageController.GetRoute {
     static func forkedFromInfo(on database: Database, fork: Fork?) async -> Model.ForkedFromInfo? {
         guard let forkedFrom = fork else { return nil }
         switch forkedFrom {
-            case let .parentId(id):
-                return await Model.ForkedFromInfo.query(on: database, packageId: id)
+            case .parentId(let id, let fallbackURL):
+                return await Model.ForkedFromInfo.query(on: database, packageId: id, fallbackURL: fallbackURL)
             case let .parentURL(url):
                 return .fromGitHub(url: url)
         }
@@ -100,15 +100,15 @@ extension API.PackageController.GetRoute {
 
 
 extension API.PackageController.GetRoute.Model.ForkedFromInfo {
-    static func query(on database: Database, packageId: Package.Id) async -> Self? {
+    static func query(on database: Database, packageId: Package.Id, fallbackURL: String) async -> Self? {
         let model = try? await Joined3<Package, Repository, Version>
             .query(on: database, packageId: packageId, version: .defaultBranch)
             .first()
 
         guard let repoName = model?.repository.name,
               let ownerName = model?.repository.ownerName,
               let owner = model?.repository.owner else {
-            return nil
+            return .fromGitHub(url: fallbackURL)
         }
 
         return .fromSPI(originalOwner: owner,

Tests/AppTests/API+PackageController+GetRoute+ModelTests.swift

@@ -132,7 +132,7 @@ class API_PackageController_GetRoute_ModelTests: SnapshotTestCase {
             .save(on: app.db)
 
         // MUT
-        let forkedFrom = await API.PackageController.GetRoute.Model.ForkedFromInfo.query(on: app.db, packageId: .id0)
+        let forkedFrom = await API.PackageController.GetRoute.Model.ForkedFromInfo.query(on: app.db, packageId: .id0, fallbackURL: "https://github.com/original/original.git")
 
         // validate
         XCTAssertEqual(forkedFrom, .fromSPI(originalOwner: "original",
@@ -141,6 +141,15 @@ class API_PackageController_GetRoute_ModelTests: SnapshotTestCase {
                                             originalPackageName: "OriginalPkg"))
     }
 
+    func test_ForkedFromInfo_query_fallback() async throws {
+        // when the package can't be found resort to fallback URL
+        // MUT
+        let forkedFrom = await API.PackageController.GetRoute.Model.ForkedFromInfo.query(on: app.db, packageId: .id0, fallbackURL: "https://github.com/original/original.git")
+
+        // validate
+        XCTAssertEqual(forkedFrom, .fromGitHub(url: "https://github.original/original.git"))
+    }
+
     func test_gitHubOwnerUrl() throws {
         var model = API.PackageController.GetRoute.Model.mock
         model.repositoryOwner = "owner"