HTML rendering support for the Website service (#5)

This PR contains the work done to replace the use of static _HTML_ files with type-safe HTML rendered server-side via **Elementary** through **Hummingbird**.

To provide further details about the work done:

* Added the **Elementary** dependencies.
* Added the `IndexPage` and `ErrorPage` pages, ported from the old HTML boilerplate; removed the static files.
* Added the `RootController` controller serving GET / using the `IndexPage` page, wired into the router.
* Reworked the `NotFoundMiddleware` middleare to render `ErrorPage` page directly; non-notFound errors still propagate.
* the `FileMiddleware` middleware no longer searches for any static `index.html` file.
* Simplified the `StaticFile` enumeration, dropped unused constants and now-unnecessary throws.

Reviewed-on: rock-n-code/loud-amsterdam#5
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Services/Website/Sources/App/App+build.swift

@@ -9,10 +9,9 @@ import WebsiteCore
 /// then assembles the router, server configuration, and logger.
 /// - Parameter reader: the configuration reader the values are read from.
 /// - Returns: the configured application, ready to run as a service.
-/// - Throws: an error if the router fails to build.
 func application(
     reader: ConfigReader
-) async throws -> some ApplicationProtocol {
+) async -> some ApplicationProtocol {
     let logLevel = reader.string(
         forKey: .Log.level,
         as: Logger.Level.self,
@@ -65,9 +64,9 @@ private func logger(
 
 /// Builds the application's router.
 ///
-/// Registers, in order, the request-logging middleware, the not-found middleware that serves
-/// the error page, and the static file middleware that serves the contents of `staticFilesPath`
-/// (falling back to `index.html` for directory requests).
+/// Registers the request-logging middleware, the not-found middleware that serves the error
+/// page, and the static file middleware that serves the contents of `staticFilesPath`, then
+/// adds the `RootController` routes that render the landing page.
 /// - Parameters:
 ///   - staticFilesPath: the folder, relative to the working directory, the static files are served from.
 ///   - logLevel: the level the request-logging middleware logs at.
@@ -80,12 +79,11 @@ private func router(
 
     router.addMiddleware {
         LogRequestsMiddleware(logLevel)
-        NotFoundMiddleware(staticFilesPath)
-        FileMiddleware(
-            staticFilesPath,
-            searchForIndexHtml: true
-        )
+        NotFoundMiddleware()
+        FileMiddleware(staticFilesPath)
     }
 
+    router.addRoutes(RootController<AppRequestContext>().routes)
+
     return router
 }