refactor: rename src folder with app

app/serializers/link.cr

@@ -0,0 +1,19 @@
+require "json"
+
+require "../models/link"
+
+module App::Serializers
+  class Link
+    def initialize(@link : App::Models::Link)
+    end
+
+    def to_json(builder : JSON::Builder)
+      builder.object do
+        builder.field("id", @link.id)
+        builder.field("link", "#{ENV["APP_URL"]}/#{@link.slug}")
+        builder.field("clicks", @link.click_counter)
+        builder.field("origin", @link.url)
+      end
+    end
+  end
+end