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/Library/Internal/Enumerations/StaticFile.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 /// A static file shipped with the website service.
 ///
 /// Each case identifies a file stored under the static files root (the `Resources/Static`
@@ -7,16 +5,12 @@ import Foundation
 enum StaticFile: CaseIterable, Sendable {
     /// The `js/app.js` script.
     case appJS
-    /// The `404.html` error page.
-    case errorHTML
     /// The `favicon.ico` icon.
     case faviconICO
     /// The `icon.png` icon.
     case iconPNG
     /// The `icon.svg` icon.
     case iconSVG
-    /// The `index.html` landing page.
-    case indexHTML
     /// The `robots.txt` crawler directives.
     case robotsTXT
     /// The `site.webmanifest` web application manifest.
@@ -32,8 +26,6 @@ extension StaticFile {
     enum Extension: String, Sendable {
         /// A Cascading Style Sheets file.
         case css
-        /// A HyperText Markup Language file.
-        case html
         /// A JavaScript file.
         case js
         /// A Portable Network Graphics image.
@@ -59,7 +51,6 @@ extension StaticFile {
     var contentType: String {
         switch fileExtension {
         case .css: "text/css"
-        case .html: "text/html"
         case .js: "text/javascript"
         case .png: "image/png"
         case .ico: "image/vnd.microsoft.icon"
@@ -74,8 +65,6 @@ extension StaticFile {
         switch self {
         case .styleCSS: .css
         case .appJS: .js
-        case .errorHTML,
-             .indexHTML: .html
         case .faviconICO: .ico
         case .iconPNG: .png
         case .iconSVG: .svg
@@ -88,11 +77,9 @@ extension StaticFile {
     var fileName: String {
         switch self {
         case .appJS: "app"
-        case .errorHTML: "404"
         case .faviconICO: "favicon"
         case .iconPNG,
              .iconSVG: "icon"
-        case .indexHTML: "index"
         case .robotsTXT: "robots"
         case .siteWebmanifest: "site"
         case .styleCSS: "style"
@@ -103,18 +90,10 @@ extension StaticFile {
     ///
     /// This also matches the URL path the file is served at by `FileMiddleware`.
     var relativePath: String {
-        let file = String(
-            format: Constant.Format.file,
-            fileName,
-            fileExtension.rawValue
-        )
+        let file = "\(fileName).\(fileExtension.rawValue)"
 
         return subdirectory
-            .map { .init(
-                format: Constant.Format.path,
-                $0,
-                file
-            )} ?? file
+            .map { "\($0)/\(file)" } ?? file
     }
 
     // MARK: Methods
@@ -129,12 +108,8 @@ extension StaticFile {
         guard !basePath.isEmpty else {
             return relativePath
         }
-        
-        return .init(
-            format: Constant.Format.path,
-            basePath,
-            relativePath
-        )
+
+        return "\(basePath)/\(relativePath)"
     }
 
 }
@@ -155,12 +130,3 @@ private extension StaticFile {
     }
 
 }
-
-// MARK: - Constants
-
-private enum Constant {
-    enum Format {
-        static let file = "%@.%@"
-        static let path = "%@/%@"
-    }
-}