SendGrid: Set to field when using merge_data (#14)

* Set to field when using merge_data

The `to` field is required even if providing recipient addresses in x-smtpapi. See https://sendgrid.com/docs/API_Reference/Web_API/mail.html#-send.

* Check data['to'] contains expected emails

* Add space for toname check

* Make `to` expected data contain email only

anymail/backends/sendgrid.py

@@ -100,6 +100,7 @@ def serialize_data(self):
             self.set_recipients('to', self.to_list)
         else:
             # Merge-friendly smtpapi 'to' field
+            self.set_recipients('to', self.to_list)
             self.smtpapi['to'] = [email.address for email in self.to_list]
             self.all_recipients += self.to_list
 

tests/test_sendgrid_backend.py

@@ -431,8 +431,8 @@ def test_merge_data(self):
 
         data = self.get_api_call_data()
         smtpapi = self.get_smtpapi()
-        self.assertNotIn('to', data)  # recipients should be moved to smtpapi-to with merge_data
-        self.assertNotIn('toname', data)
+        self.assertEqual(data['toname'], [' ', 'Bob'])
+        self.assertEqual(data['to'], ['alice@example.com', 'bob@example.com'])
         self.assertEqual(smtpapi['to'], ['alice@example.com', 'Bob <bob@example.com>'])
         self.assertEqual(smtpapi['sub'], {
             ':name': ["Alice", "Bob"],