Implemented phase 2 for the POC prototype in the Website service.

Services/Website/Tests/App/AppTests.swift

@@ -97,6 +97,36 @@ struct AppTests {
         }
     }
 
+    @Test
+    func `sign-in to start a session the other pages recognize`() async throws {
+        try await app(
+            staticFilesPath: staticFilesPath
+        ).test(.router) { client in
+            let cookie = try await client.execute(
+                uri: "/sign-in",
+                method: .post,
+                headers: [.contentType: "application/x-www-form-urlencoded"],
+                body: ByteBuffer(string: "return=/listing/nightward-1-cgc-9-8")
+            ) { response in
+                #expect(response.status == .seeOther)
+                #expect(response.headers[.location] == "/listing/nightward-1-cgc-9-8")
+
+                return String(try #require(response.headers[.setCookie]).prefix { $0 != ";" })
+            }
+
+            try await client.execute(
+                uri: "/listing/nightward-1-cgc-9-8",
+                method: .get,
+                headers: [.cookie: cookie]
+            ) { response in
+                let body = String(buffer: response.body)
+
+                #expect(body.contains(#"aria-label="Account of Mara Visser""#))
+                #expect(body.contains(#"href="/listing/nightward-1-cgc-9-8/offer""#))
+            }
+        }
+    }
+
     @Test
     func `error page to be served for an unknown listing`() async throws {
         try await app(