add ability to use timestamp server

app/controllers/timestamp_server_controller.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+class TimestampServerController < ApplicationController
+  before_action :build_encrypted_config
+  authorize_resource :encrypted_config
+
+  def create
+    return head :not_found if Docuseal.multitenant?
+
+    test_timeserver_url(@encrypted_config.value) if @encrypted_config.value.present?
+
+    if @encrypted_config.value.present? ? @encrypted_config.save : @encrypted_config.delete
+      redirect_back fallback_location: settings_notifications_path, notice: 'Changes have been saved'
+    else
+      redirect_back fallback_location: settings_notifications_path, alert: 'Unable to save'
+    end
+  rescue HexaPDF::Error, SocketError, Submissions::TimestampHandler::TimestampError
+    redirect_back fallback_location: settings_notifications_path, alert: 'Invalid Timeserver'
+  end
+
+  private
+
+  def test_timeserver_url(url)
+    pdf = HexaPDF::Document.new
+    pdf.pages.add
+
+    pkcs = Accounts.load_signing_pkcs(current_account)
+
+    pdf.sign(StringIO.new,
+             reason: 'Test',
+             certificate: pkcs.certificate,
+             key: pkcs.key,
+             certificate_chain: pkcs.ca_certs || [],
+             timestamp_handler: Submissions::TimestampHandler.new(tsa_url: url))
+  end
+
+  def load_encrypted_config
+    @encrypted_config
+  end
+
+  def build_encrypted_config
+    @encrypted_config =
+      EncryptedConfig.find_or_initialize_by(account: current_account,
+                                            key: EncryptedConfig::TIMESTAMP_SERVER_URL_KEY)
+
+    @encrypted_config.assign_attributes(encrypted_config_params)
+  end
+
+  def encrypted_config_params
+    params.require(:encrypted_config).permit(:value)
+  end
+end