Fix: options included in the headers

The call to `except` here should not be an array as there is no array of
these symbol to exclude from the hash.

This issue was kindly identified by @inulty-dfe in #162.

lib/mail/notify/mailer.rb

@@ -38,7 +38,7 @@ def template_mail(template_id, options)
 
         message.personalisation = options[:personalisation] || {}
 
-        headers = options.except([:personalisation, :reply_to_id, :reference])
+        headers = options.except(:personalisation, :reply_to_id, :reference)
 
         headers[:subject] = "Subject managed in Notify" unless options[:subject]
 
@@ -74,7 +74,7 @@ def view_mail(template_id, options)
         message.reference = options[:reference]
 
         subject = options[:subject]
-        headers = options.except([:personalisation, :reply_to_id, :reference])
+        headers = options.except(:personalisation, :reply_to_id, :reference)
 
         # we have to render the view for the message and grab the raw source, then we set that as the
         # body in the personalisation for sending to the Notify API.

spec/mail/notify/mailer_spec.rb

@@ -115,6 +115,23 @@
         ArgumentError, "You must specify a subject"
       )
     end
+
+    it "does not include the personalisation, reply_to_id or reference options in the headers" do
+      message_params = {
+        template_id: "template-id",
+        to: "[email protected]",
+        subject: "Test subject",
+        personalisation: "test-personalisation",
+        reply_to_id: "[email protected]",
+        reference: "test-reference"
+      }
+
+      message = TestMailer.with(message_params).test_view_mail
+
+      expect(message.header[:personalisation]).to be_nil
+      expect(message.header[:reply_to_id]).to be_nil
+      expect(message.header[:reference]).to be_nil
+    end
   end
 
   describe "#template_email" do
@@ -202,6 +219,23 @@
 
       expect(message.reference).to eql("test-reference")
     end
+
+    it "does not include the personalisation, reply_to_id or reference options in the headers" do
+      message_params = {
+        template_id: "template-id",
+        to: "[email protected]",
+        subject: "Test subject",
+        personalisation: "test-personalisation",
+        reply_to_id: "[email protected]",
+        reference: "test-reference"
+      }
+
+      message = TestMailer.with(message_params).test_template_mail
+
+      expect(message.header[:personalisation]).to be_nil
+      expect(message.header[:reply_to_id]).to be_nil
+      expect(message.header[:reference]).to be_nil
+    end
   end
 
   describe "#blank_allowed" do