implement amendment signing

app/models/concerns/amendmenable.rb

@@ -0,0 +1,27 @@
+module Amendmenable
+  extend ActiveSupport::Concern
+
+  included do
+    include ActiveStorageSupport::SupportForBase64
+
+    has_one_base64_attached :amendment_signature
+  end
+
+  def amendment_signable?
+    contract_template.amendment_clause.present?
+  end
+
+  def amendment_signed?
+    amendment_signature.attached?
+  end
+
+  def amendment_signature_base64
+    nil
+  end
+
+  def amendment_signature_base64=(data_uri)
+    return if data_uri.blank?
+
+    amendment_signature.attach(data: data_uri, filename: "amendment_signature.png", content_type: "image/png", identify: "false")
+  end
+end