air-email-review: fix occasionally missing CCs

We occasionally miss the CC field of the original email when sending
the reply (most notably that usually means we don't CC the ML).

Turns out Patchwork returns headers with "CC" or "Cc". Check for all
sensible capitalization.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

air-email-review.py

@@ -340,12 +340,16 @@ def extract_recipients(patch_info_list: List[Dict]) -> Tuple[List[str], List[str
         headers = patch_info.get('headers', {})
         if isinstance(headers, dict):
             # Parse To header
-            to_header = headers.get('To', '')
+            to_header = headers.get('to', '') or \
+                        headers.get('To', '') or \
+                        headers.get('TO', '')
             for addr in parse_email_list(to_header):
                 cc_set.add(addr)
 
-            # Parse Cc header
-            cc_header = headers.get('Cc', '')
+            # Parse Cc header (API may return 'Cc' or 'CC')
+            cc_header = headers.get('cc', '') or \
+                        headers.get('Cc', '') or \
+                        headers.get('CC', '')
             for addr in parse_email_list(cc_header):
                 cc_set.add(addr)