Project updates from Template (#1)

This PR contains the latest updates from the generic Website template, which have been added while working on #loud-amsterdam.

Reviewed-on: #1
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Services/Website/Sources/Library/Public/Controllers/RootController.swift

@@ -25,15 +25,18 @@ public struct RootController<Context: LocalizedRequestContext> {
     /// Creates a root controller.
     /// - Parameters:
     ///   - assetVersion: the version token appended to the page's asset URLs, or `nil` (the default) to leave them unversioned.
+    ///   - siteOrigin: the public origin the page derives its canonical URL and language alternates from, or `nil` (the default) to omit them.
     ///   - analytics: the analytics tracker the landing page embeds, or `nil` (the default) to omit it.
     public init(
         assetVersion: String? = nil,
+        siteOrigin: String? = nil,
         analytics: Analytics? = nil
     ) {
         self.responses = .init(bundle: .module) {
             IndexPage(
                 locale: $0,
                 assetVersion: assetVersion,
+                siteOrigin: siteOrigin,
                 analytics: analytics
             )
         }
@@ -55,6 +58,15 @@ extension RootController: RouterController {
             use: index
         )
 
+        // Every non-default language answers under a prefix of its own, so the `hreflang` alternates the page advertises
+        // resolve and a crawler can index each edition at a stable URL. A single-language catalog adds none.
+        for language in Language.all where !language.isDefault {
+            routes.get(
+                .init(language.path(IndexPage.path)),
+                use: index(in: language)
+            )
+        }
+
         return routes
     }
 
@@ -84,6 +96,23 @@ private extension RootController {
         )
     }
 
+    /// Builds the handler serving the landing page in one fixed language, for the routes carrying the language in their path.
+    ///
+    /// The path *is* the language choice, so the negotiated context language is ignored: a prefixed URL answers in its language for every
+    /// visitor and every crawler alike, which is what lets a search engine index it as that edition.
+    /// - Parameter language: the language the route serves.
+    /// - Returns: the handler answering requests for that edition of the page.
+    func index(
+        in language: Language
+    ) -> @Sendable (Request, Context) -> Response {
+        { request, _ in
+            responses.response(
+                for: language.identifier,
+                request: request
+            )
+        }
+    }
+
 }
 
 // MARK: - Constants
@@ -91,7 +120,7 @@ private extension RootController {
 private extension RouterPath {
     /// A namespace for the ``RootController`` route paths.
     enum Root {
-        /// The path of the landing page.
-        static let index: RouterPath = "/"
+        /// The path of the landing page; the page builds its canonical URL from the same constant.
+        static let index: RouterPath = .init(IndexPage.path)
     }
 }