Extra tags and Social Card integration in the Infrastructure package (#28)

This PR contains the work done to extends the `Page` protocol with the head tags that control search snippets and link previews: a meta description, a canonical URL, and a social card rendered as _Open Graph_ and _Twitter_ meta tags. All three are optional with nil defaults, so existing conformers compile and render unchanged.

Reviewed-on: rock-n-code/loud-amsterdam#28
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Packages/Infrastructure/Tests/Utils/Extensions/Tag+Constants.swift

@@ -9,6 +9,6 @@ extension Tag {
     @Tag static var middleware: Tag
     /// Tests exercising a protocol scaffolding of the Infrastructure package.
     @Tag static var `protocol`: Tag
-    /// Tests exercising an internal type of the Infrastructure package.
+    /// Tests exercising a type of the Infrastructure package.
     @Tag static var type: Tag
 }

Packages/Infrastructure/Tests/Utils/Pages/StubPage.swift

@@ -10,9 +10,18 @@ struct StubPage: Page {
     /// The version token appended to the page's asset URLs, or `nil` to leave them unversioned.
     let assetVersion: String?
 
+    /// The canonical URL rendered in the document head, or `nil` to omit it.
+    let canonicalURL: String?
+
     /// The locale the page content is localized to.
     let locale: Locale
 
+    /// The card rendered as link-preview tags in the document head, or `nil` to omit them.
+    let socialCard: SocialCard?
+
+    /// The summary rendered in the document head, or `nil` to omit it.
+    let summary: String?
+
     // MARK: Initializers
 
     /// Creates a stub page.
@@ -20,12 +29,24 @@ struct StubPage: Page {
     ///   - locale: the locale the page content is localized to. Defaults to `en`.
     ///   - assetVersion: the version token appended to the page's asset URLs, or `nil` (the
     ///     default) to leave them unversioned.
+    ///   - canonicalURL: the canonical URL rendered in the document head, or `nil` (the default)
+    ///     to omit it.
+    ///   - socialCard: the card rendered as link-preview tags in the document head, or `nil`
+    ///     (the default) to omit them.
+    ///   - summary: the summary rendered in the document head, or `nil` (the default)
+    ///     to omit it.
     init(
         locale: Locale = .init(identifier: "en"),
-        assetVersion: String? = nil
+        assetVersion: String? = nil,
+        canonicalURL: String? = nil,
+        socialCard: SocialCard? = nil,
+        summary: String? = nil
     ) {
         self.assetVersion = assetVersion
+        self.canonicalURL = canonicalURL
         self.locale = locale
+        self.socialCard = socialCard
+        self.summary = summary
     }
 
     // MARK: Computed