Added a configurable site origin to the ConfigReader+Properties extension in the Website library target.

Services/Website/Sources/App/Extensions/ConfigReader+Properties.swift

@@ -240,6 +240,17 @@ package extension ConfigReader {
         )
     }
 
+    /// The public origin the site is served at (scheme and host, no trailing slash), read from the `site.origin` key.
+    ///
+    /// The redirects and any absolute links derive from it, so a staging deployment can point it at itself — or leave it unset — without the
+    /// production origin leaking into its markup.
+    var siteOrigin: String {
+        string(
+            forKey: .Site.origin,
+            default: .Site.origin
+        )
+    }
+
     /// The directory the static files are served from, read from the `path.staticFiles` key.
     var staticFilesPath: String {
         string(

Services/Website/Sources/Library/Public/Extensions/ConfigKey+Constants.swift

@@ -98,4 +98,9 @@ extension ConfigKey {
         /// The configuration key for the `Strict-Transport-Security` header value (omitted when unset).
         public static let strictTransportSecurity: ConfigKey = "security.strictTransportSecurity"
     }
+    /// A namespace for the site configuration keys.
+    public enum Site {
+        /// The configuration key for the public origin the site is served at (scheme and host, no trailing slash).
+        public static let origin: ConfigKey = "site.origin"
+    }
 }

Services/Website/Sources/Library/Public/Extensions/String+Constants.swift

@@ -50,4 +50,12 @@ extension String {
         /// The website server's name.
         public static let name = "SiteWebsite"
     }
+    /// A namespace for the site string constants.
+    public enum Site {
+        /// The default public origin the site is served at (scheme and host, no trailing slash): empty, which leaves the HTTPS redirect off.
+        ///
+        /// A deployment that trusts the forwarded-protocol header without also setting `site.origin` would otherwise redirect at a host the
+        /// template guessed for it, and a `301` is cached for a long time.
+        public static let origin = ""
+    }
 }