add ability to use own signing cert

app/controllers/verify_pdf_signature_controller.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+class VerifyPdfSignatureController < ApplicationController
+  def create
+    pdfs =
+      params[:files].map do |file|
+        HexaPDF::Document.new(io: file.open)
+      end
+
+    cert_data = EncryptedConfig.find_by(account: current_account,
+                                        key: EncryptedConfig::ESIGN_CERTS_KEY)&.value || {}
+
+    default_pkcs = GenerateCertificate.load_pkcs(cert_data)
+
+    custom_certs = (cert_data['custom'] || []).map do |e|
+      OpenSSL::PKCS12.new(Base64.urlsafe_decode64(e['data']), e['password'])
+    end
+
+    trusted_certs = [default_pkcs.certificate,
+                     *default_pkcs.ca_certs,
+                     *custom_certs.map(&:certificate),
+                     *custom_certs.flat_map(&:ca_certs).compact]
+
+    render turbo_stream: turbo_stream.replace('result', partial: 'result',
+                                                        locals: { pdfs:, files: params[:files], trusted_certs: })
+  rescue HexaPDF::MalformedPDFError
+    render turbo_stream: turbo_stream.replace('result', html: helpers.tag.div('Invalid PDF', id: 'result'))
+  end
+end