Postmark inbound: Fix ValueError with long, non-ASCII name

Receiving a Postmark inbound message with a long From or recipient Name field could result
in "ValueError: Header values may not contain linefeed or carriage return characters" if
the name included non-ASCII characters.

Anymail's EmailAddress calls Django's sanitize_address(), which can introduce folding
whitespace, causing an error in the AnymailInboundMessage constructor. Only Postmark inbound
is affected, as no other webhooks construct an EmailAddress.

(Longer-term, Anymail should stop using the undocumented Django sanitize_address.)

CHANGELOG.rst

@@ -53,6 +53,9 @@ Fixes
   "queued" in the ``anymail_status`` (rather than throwing an error or reporting
   "sent"). (Thanks to `@jmduke`_ for reporting the issue.)
 
+* **Postmark:** Fix an error in inbound handling with long email address display
+  names that include non-ASCII characters.
+
 
 v12.0
 -----

anymail/utils.py

@@ -1,5 +1,6 @@
 import base64
 import mimetypes
+import re
 from base64 import b64encode
 from collections.abc import Mapping, MutableMapping
 from copy import copy, deepcopy
@@ -342,7 +343,10 @@ def formataddr(self, encoding=None):
             default None uses ascii if possible, else 'utf-8'
             (quoted-printable utf-8/base64)
         """
-        return sanitize_address((self.display_name, self.addr_spec), encoding)
+        sanitized = sanitize_address((self.display_name, self.addr_spec), encoding)
+        # sanitize_address() can introduce FWS with a long, non-ASCII display name.
+        # Must unfold it:
+        return re.sub(r"(\r|\n|\r\n)[ \t]", "", sanitized)
 
     def __str__(self):
         return self.address

tests/test_postmark_inbound.py

@@ -392,3 +392,32 @@ def test_check_payload(self):
                 )
                 # Don't care about the actual test message contents here,
                 # just want to make sure it parses and signals inbound without error.
+
+    def test_spammy_address(self):
+        # This long FromFull.Name caused an error in AnymailInboundMessage construction,
+        # due to folding introduced in EmailAddress.formataddr()
+        from_name = (
+            "* * * 💲 Snag Your Free Gift! Click Here: "
+            "https://spam.example.com/uploads/phish.php?123456 💲 * * *"
+        )
+        raw_event = {
+            "MessageStream": "inbound",
+            "FromFull": {
+                "Email": "noreply@spam.example.com",
+                "Name": from_name,
+            },
+        }
+        response = self.client.post(
+            "/anymail/postmark/inbound/",
+            content_type="application/json",
+            data=json.dumps(raw_event),
+        )
+        self.assertEqual(response.status_code, 200)
+        kwargs = self.assert_handler_called_once_with(
+            self.inbound_handler,
+            sender=PostmarkInboundWebhookView,
+            event=ANY,
+            esp_name="Postmark",
+        )
+        message = kwargs["event"].message
+        self.assertEqual(message.from_email.display_name, from_name)