Implemented phase 1 for the POC prototype in the Website service.

Services/Website/Tests/Library/Utils/Stubs/Listing+Stub.swift

@@ -0,0 +1,44 @@
+import Foundation
+import Persistence
+
+extension Listing {
+    /// A listing for tests: a slabbed single issue unless told otherwise.
+    static func stub(
+        slug: String = "nightward-1",
+        shop: Shop = .stub(),
+        title: String = "Nightward #1",
+        format: String = "single-issues",
+        grader: String? = "CGC",
+        grade: Double? = 9.8,
+        condition: String = "NM/M",
+        keyNotes: String? = nil,
+        priceCents: Int = 24_000,
+        acceptsOffers: Bool = true
+    ) -> Self {
+        .init(
+            slug: slug, shop: shop, title: title, seriesTitle: "Nightward (2019 series)", issueLabel: "#1",
+            publisher: "Meridian Comics", year: 2019, format: format, printing: "1st print",
+            printingDetail: "First printing", isFirstPrint: true, grader: grader, grade: grade,
+            condition: condition, certNumber: grader == nil ? nil : "4312087-002", pageQuality: "White",
+            keyNotes: keyNotes, sellerNotes: "Clean case.", priceCents: priceCents, shippingCents: 600,
+            acceptsOffers: acceptsOffers,
+            cover: .init(tone: "navy", title: "NIGHT\nWARD", imprint: "MERIDIAN", number: "1"),
+            listedAt: .init(timeIntervalSince1970: 0)
+        )
+    }
+}
+
+extension Shop {
+    /// A shop for tests: a verified Amsterdam seller unless told otherwise.
+    static func stub(
+        slug: String = "kestrel-row-comics",
+        name: String = "Kestrel Row Comics",
+        isVerified: Bool = true
+    ) -> Self {
+        .init(
+            slug: slug, name: name, city: "Amsterdam", country: "NL", sinceYear: 2023, isVerified: isVerified,
+            rating: 4.9, ratedSales: 312, soldCount: 1108, handlingDays: 2, shipsNote: "ships worldwide, tracked",
+            returnsNote: "14-day returns", about: "Modern keys."
+        )
+    }
+}