Added language support to the Website service target.

Services/Website/Sources/App/Extensions/App+Build.swift

@@ -57,6 +57,9 @@ func application(
             httpsRedirect: reader.httpsRedirect,
             rateLimit: reader.rateLimit,
             securityHeaders: reader.securityHeaders,
+            // An unset origin leaves the pages without canonical URLs and language alternates, rather than
+            // building both against an empty host.
+            siteOrigin: reader.siteOrigin.isEmpty ? nil : reader.siteOrigin,
             logLevel: reader.logLevel,
             probe: Probe(fluent: fluent)
         ),
@@ -141,9 +144,10 @@ private func logger(
 /// HTTPS-redirect middleware that bounces requests forwarded over plain HTTP to the canonical origin, the trailing-slash redirect middleware that
 /// collapses each path onto its canonical form, the vary middleware that marks every response as varying on `Accept-Encoding`, the response-compression middleware that compresses responses
 /// larger than `minimumResponseSizeToCompress` when the client advertises support, the localization middleware that negotiates the request's
-/// language from its `Accept-Language` header, the not-found middleware that serves the not-found page, and the static file middleware that serves the
+/// language from its `Accept-Language` header (honouring the `lang` query override and the language a leading path segment names), the
+/// not-found middleware that serves the not-found page, and the static file middleware that serves the
 /// contents of `staticFilesPath` (tagging responses with the given `cacheControl` directives), then adds the `RootController` routes that
-/// render the landing page, and the `HealthController` routes that serve the health check.
+/// render the landing page — one per language the String Catalog serves — and the `HealthController` routes that serve the health check.
 ///
 /// The security-headers middleware sits just inside request logging so it covers every response that reaches a client — the landing page, the compressed
 /// responses, the rendered not-found page, and the served static files. The HTTPS redirect sits directly beneath it, so a redirect carries the security
@@ -158,6 +162,7 @@ private func logger(
 ///   - httpsRedirect: the origin plain-HTTP requests are redirected to, and whether the forwarded-protocol header is trusted.
 ///   - rateLimit: the rate limit configuration, currently applied to no route.
 ///   - securityHeaders: the security headers applied to every response.
+///   - siteOrigin: the public origin the pages derive their canonical URLs and language alternates from, or `nil` to omit them.
 ///   - logLevel: the level the request-logging middleware logs at.
 ///   - probe: the probe consulted by the `HealthController` readiness route.
 /// - Returns: the configured router.
@@ -170,6 +175,7 @@ private func router(
     httpsRedirect: HTTPSRedirectMiddleware<AppRequestContext>.Configuration,
     rateLimit: RateLimitMiddleware<AppRequestContext>.Configuration,
     securityHeaders: SecurityHeadersMiddleware<AppRequestContext>.Configuration,
+    siteOrigin: String?,
     logLevel: Logger.Level,
     probe: Probe
 ) -> Router<AppRequestContext> {
@@ -207,6 +213,7 @@ private func router(
     router.addController {
         RootController<AppRequestContext>(
             assetVersion: assetVersion,
+            siteOrigin: siteOrigin,
             analytics: analytics
         )
         HealthController<AppRequestContext>(