feat: Name the app's version and project in its user agent

Sources/ScrollkeeperKit/Networking/URLSessionHTTPClient.swift

@@ -18,7 +18,7 @@ public final class URLSessionHTTPClient: HTTPClient {
         configuration.urlCache = nil
         configuration.requestCachePolicy = .reloadIgnoringLocalCacheData
         configuration.timeoutIntervalForRequest = 180
-        configuration.httpAdditionalHeaders = ["User-Agent": userAgent]
+        configuration.httpAdditionalHeaders = ["User-Agent": userAgent(version: appVersion)]
         return configuration
     }
 
@@ -68,8 +68,17 @@ public final class URLSessionHTTPClient: HTTPClient {
         (response as? HTTPURLResponse)?.statusCode ?? 0
     }
 
-    private static let userAgent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 "
-        + "(KHTML, like Gecko) Version/18.0 Safari/605.1.15 Scrollkeeper/1.0"
+    /// Safari's user agent, so paizo.com treats the app like a browser, then the app's name, version and project
+    /// page, so Paizo can tell its requests apart, measure them and block them if it ever has to.
+    static func userAgent(version: String) -> String {
+        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 "
+            + "Safari/605.1.15 Scrollkeeper/\(version) (+https://github.com/scooper4711/scrollkeeper)"
+    }
+
+    /// The running app's version; "0" where there is no app bundle, as in the unit tests.
+    private static var appVersion: String {
+        Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "0"
+    }
 }
 
 /// Reports the fraction completed of one download task.

Tests/ScrollkeeperKitTests/SystemIntegrationTests.swift

@@ -77,6 +77,13 @@ final class StubURLProtocol: URLProtocol {
         #expect(configuration.urlCache == nil)
         #expect(configuration.requestCachePolicy == .reloadIgnoringLocalCacheData)
     }
+
+    @Test func userAgentNamesTheAppItsVersionAndItsProjectAfterSafari() {
+        let agent = URLSessionHTTPClient.userAgent(version: "1.4.2")
+        #expect(agent.hasPrefix("Mozilla/5.0 "))
+        #expect(agent.contains(" Safari/"))
+        #expect(agent.hasSuffix(" Scrollkeeper/1.4.2 (+https://github.com/scooper4711/scrollkeeper)"))
+    }
 }
 
 @Suite struct ResumeDataStoreTests {

docs/specs/library-manager/design.md

@@ -130,6 +130,9 @@ Views ──► LibraryStore ──► CatalogSynchronizer ──► LibraryCata
 
 - `HTTPClient` — protocol with `send(_:)` and `download(_:to:progress:)`.
   `URLSessionHTTPClient` is the production implementation; tests use a stub.
+  Its user agent is Safari's, so paizo.com serves the app as it serves a
+  browser, followed by `Scrollkeeper/<CFBundleShortVersionString>
+  (+https://github.com/scooper4711/scrollkeeper)` (requirement 9.4).
 - `PaizoSession` — actor. Signs in and hands out customer tokens, reusing one
   until shortly before the expiry it carries.
 - `FlightPayloadParser` — extracts the `LibraryPage` from library page HTML.

docs/specs/library-manager/requirements.md

@@ -202,6 +202,9 @@ once, online or off.
 9.2 No account data, tokens or credentials are written to logs or committed to
     the repository.
 9.3 The app does not change anything on the Paizo account.
+9.4 Every request names the app, its version and its project page in the user
+    agent, after Safari's, so Paizo can tell the app's traffic apart, measure
+    it and block it if it ever has to.
 
 ## 10. iPad