Use config.domain in place of hardcoded value

src/invidious/helpers/helpers.cr

@@ -15,7 +15,10 @@ class Config
     https_only:   Bool?,
     hmac_key:     String?,
     full_refresh: Bool,
-    domain:       String?,
+    domain:       {
+      type:    String?,
+      default: "invidio.us",
+    },
   })
 end
 

src/invidious/helpers/utils.cr

@@ -205,8 +205,6 @@ def make_host_url(ssl, host)
     scheme = "http://"
   end
 
-  host ||= "invidio.us"
-
   return "#{scheme}#{host}"
 end