Bring app in line with Hanami 2.1.0 base

app/relations/webmentions.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Adamantium
+  module Relations
+    class Webmentions < ROM::Relation[:sql]
+      schema :webmentions, infer: true do
+        associations do
+          belongs_to :post
+        end
+      end
+
+      auto_struct(true)
+
+      def published
+        where(self[:published_at] <= Time.now)
+      end
+    end
+  end
+end