add default user signatures

app/controllers/user_signatures_controller.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+class UserSignaturesController < ApplicationController
+  before_action :load_user_config
+  authorize_resource :user_config
+
+  def edit; end
+
+  def update
+    file = params[:file]
+
+    return redirect_to settings_profile_index_path, notice: 'Unable to save signature' if file.blank?
+
+    blob = ActiveStorage::Blob.create_and_upload!(io: file.open,
+                                                  filename: file.original_filename,
+                                                  content_type: file.content_type)
+
+    attachment = ActiveStorage::Attachment.create!(
+      blob:,
+      name: 'signature',
+      record: current_user
+    )
+
+    if @user_config.update(value: attachment.uuid)
+      redirect_to settings_profile_index_path, notice: 'Signature has been saved'
+    else
+      redirect_to settings_profile_index_path, notice: 'Unable to save signature'
+    end
+  end
+
+  private
+
+  def load_user_config
+    @user_config =
+      UserConfig.find_or_initialize_by(user: current_user, key: UserConfig::SIGNATURE_KEY)
+  end
+end