add developer newsletters form

app/controllers/newsletters_controller.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+class NewslettersController < ApplicationController
+  def show; end
+
+  def update
+    Faraday.post(Docuseal::NEWSLETTER_URL, newsletter_params.to_json, 'Content-Type' => 'application/json')
+  rescue StandardError => e
+    Rails.logger.error(e)
+  ensure
+    redirect_to root_path
+  end
+
+  private
+
+  def newsletter_params
+    params.require(:user).permit(:email)
+  end
+end