Added the Utility package (#29)

This PR contains the work done to create the new **Utility** package within the project, and also included in it the `NormalizeEmail` method, as it's not something that belongs to the **Infrastructure** package.

Reviewed-on: rock-n-code/loud-amsterdam#29
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Infrastructure/README.md

@@ -8,13 +8,14 @@ The package provides, grouped by role:
 | Routing | `RouterController`, `RouteCollectionBuilder`, the `addController` extension on `RouterMethods` |
 | Middlewares | `SecurityHeadersMiddleware`, `VaryMiddleware`, `RateLimitMiddleware`, `LocalizationMiddleware`, `NotFoundMiddleware` |
 | Pages and assets | `Page`, `Asset`, `AssetExtension`, `FingerprintAssets` |
+| Link previews | `SocialCard`, its `Image`, and the `SocialCardTag` meta tags it derives |
 | Responses | `CachedHTMLResponse`, `LocalizedHTMLCollectionResponse` |
 | Contexts | `LocalizedRequestContext` |
 | Constants | The `HTTPField.Name` header names, `Int.RateLimit` limits, and `String.Security` header values the middlewares default to |
 
 ## Design rules
 The package holds only what every service can reuse; anything a service owns is injected, never referenced:
-- **No site-specific content.** No page markup, no asset catalog, no `Bundle.module` lookups. A type that needs a service's content takes it as a parameter: the `bundle:` whose String Catalog names the supported languages (`LocalizationMiddleware`, `LocalizedHTMLCollectionResponse`, `NotFoundMiddleware`), the `document:` closure that builds a page for a locale, and the `metadata` requirement through which a `Page` conformer supplies its icon links and theme colors.
+- **No site-specific content.** No page markup, no asset catalog, no `Bundle.module` lookups. A type that needs a service's content takes it as a parameter: the `bundle:` whose String Catalog names the supported languages (`LocalizationMiddleware`, `LocalizedHTMLCollectionResponse`, `NotFoundMiddleware`), the `document:` closure that builds a page for a locale, and the `metadata` requirement through which a `Page` conformer supplies its icon links and theme colors — as are the `summary`, `canonicalURL`, and `socialCard` values its other head tags render, each omitted unless the page provides it. A `SocialCard` takes its URLs fully formed and absolute; composing them from an origin and a versioned asset path stays with the page providing the card.
 - **Services fill the gaps once, via extensions.** A service restores its convenient call sites with retroactive extensions — the Website's `Page+Defaults`, `LocalizationMiddleware+Defaults`, and `NotFoundMiddleware+Defaults` are the pattern to follow.
 - **Method structs.** Single-operation types such as `FingerprintAssets` hold their lifetime-fixed configuration in `init` and take only per-call inputs in `callAsFunction`.
 
@@ -29,7 +30,8 @@ Sources/
 │   ├── Methods/           FingerprintAssets
 │   ├── Middlewares/       the five HTTP middlewares
 │   ├── Protocols/         Asset, LocalizedRequestContext, Page, RouterController
-│   └── Responses/         CachedHTMLResponse, LocalizedHTMLCollectionResponse
+│   ├── Responses/         CachedHTMLResponse, LocalizedHTMLCollectionResponse
+│   └── Types/             SocialCard, with its image and tag types in SocialCard/
 └── Internal/
     └── Types/             implementation details (FNV1aHash)
 Tests/
@@ -43,4 +45,4 @@ Every suite carries a tag naming the kind of API it exercises — `.asset`, `.ex
 
 ## Requirements
 - Swift 6.3 toolchain (`swift-tools-version:6.3`).
-- macOS 15, matching the sibling `Localization` and `Persistence` packages (the services deploy to Linux containers; the packages carry no UI platforms).
+- macOS 15, matching the sibling `Localization`, `Persistence`, and `Utility` packages (the services deploy to Linux containers; the packages carry no UI platforms).