feat(fcm): Support proxy field in FCM AndroidNotification (#868)

* feat(fcm): Support `proxy` field in FCM `AndroidNotification`

* fix lint

* fix: Update `proxy` and `visibility` doc string with TW suggestion

Author: jonathanedey

Diff for: firebase_admin/_messaging_encoder.py

@@ -319,7 +319,9 @@ def encode_android_notification(cls, notification):
             'visibility': _Validators.check_string(
                 'AndroidNotification.visibility', notification.visibility, non_empty=True),
             'notification_count': _Validators.check_number(
-                'AndroidNotification.notification_count', notification.notification_count)
+                'AndroidNotification.notification_count', notification.notification_count),
+            'proxy': _Validators.check_string(
+                'AndroidNotification.proxy', notification.proxy, non_empty=True)
         }
         result = cls.remove_null_values(result)
         color = result.get('color')
@@ -363,6 +365,13 @@ def encode_android_notification(cls, notification):
                     'AndroidNotification.vibrate_timings_millis', msec)
                 vibrate_timing_strings.append(formated_string)
             result['vibrate_timings'] = vibrate_timing_strings
+
+        proxy = result.get('proxy')
+        if proxy:
+            if proxy not in ('allow', 'deny', 'if_priority_lowered'):
+                raise ValueError(
+                    'AndroidNotification.proxy must be "allow", "deny" or "if_priority_lowered".')
+            result['proxy'] = proxy.upper()
         return result
 
     @classmethod

Diff for: firebase_admin/_messaging_utils.py

@@ -137,14 +137,18 @@ class AndroidNotification:
             If ``default_light_settings`` is set to ``True`` and ``light_settings`` is also set, the
             user-specified ``light_settings`` is used instead of the default value.
         visibility: Sets the visibility of the notification. Must be either ``private``, ``public``,
-            or ``secret``. If unspecified, default to ``private``.
+            or ``secret``. If unspecified, it remains undefined in the Admin SDK, and defers to
+            the FCM backend's default mapping.
         notification_count: Sets the number of items this notification represents. May be displayed
             as a badge count for Launchers that support badging. See ``NotificationBadge``
             https://developer.android.com/training/notify-user/badges. For example, this might be
             useful if you're using just one notification to represent multiple new messages but you
             want the count here to represent the number of total new messages. If zero or
             unspecified, systems that support badging use the default, which is to increment a
             number displayed on the long-press menu each time a new notification arrives.
+        proxy: Sets if the notification may be proxied. Must be one of ``allow``, ``deny``, or
+            ``if_priority_lowered``. If unspecified, it remains undefined in the Admin SDK, and
+            defers to the FCM backend's default mapping.
 
 
     """
@@ -154,7 +158,8 @@ def __init__(self, title=None, body=None, icon=None, color=None, sound=None, tag
                  title_loc_args=None, channel_id=None, image=None, ticker=None, sticky=None,
                  event_timestamp=None, local_only=None, priority=None, vibrate_timings_millis=None,
                  default_vibrate_timings=None, default_sound=None, light_settings=None,
-                 default_light_settings=None, visibility=None, notification_count=None):
+                 default_light_settings=None, visibility=None, notification_count=None,
+                 proxy=None):
         self.title = title
         self.body = body
         self.icon = icon
@@ -180,6 +185,7 @@ def __init__(self, title=None, body=None, icon=None, color=None, sound=None, tag
         self.default_light_settings = default_light_settings
         self.visibility = visibility
         self.notification_count = notification_count
+        self.proxy = proxy
 
 
 class LightSettings:

Diff for: integration/test_messaging.py

@@ -55,7 +55,8 @@ def test_send():
                     light_off_duration_millis=200,
                     light_on_duration_millis=300
                 ),
-                notification_count=1
+                notification_count=1,
+                proxy='if_priority_lowered',
             )
         ),
         apns=messaging.APNSConfig(payload=messaging.APNSPayload(

Diff for: tests/test_messaging.py

@@ -535,6 +535,20 @@ def test_invalid_visibility(self, visibility):
             expected = 'AndroidNotification.visibility must be a non-empty string.'
         assert str(excinfo.value) == expected
 
+    @pytest.mark.parametrize('proxy', NON_STRING_ARGS + ['foo'])
+    def test_invalid_proxy(self, proxy):
+        notification = messaging.AndroidNotification(proxy=proxy)
+        excinfo = self._check_notification(notification)
+        if isinstance(proxy, str):
+            if not proxy:
+                expected = 'AndroidNotification.proxy must be a non-empty string.'
+            else:
+                expected = ('AndroidNotification.proxy must be "allow", "deny" or'
+                            ' "if_priority_lowered".')
+        else:
+            expected = 'AndroidNotification.proxy must be a non-empty string.'
+        assert str(excinfo.value) == expected
+
     @pytest.mark.parametrize('vibrate_timings', ['', 1, True, 'msec', ['500', 500], [0, 'abc']])
     def test_invalid_vibrate_timings_millis(self, vibrate_timings):
         notification = messaging.AndroidNotification(vibrate_timings_millis=vibrate_timings)
@@ -580,6 +594,7 @@ def test_android_notification(self):
                         light_off_duration_millis=300,
                     ),
                     default_light_settings=False, visibility='public', notification_count=1,
+                    proxy='if_priority_lowered',
                 )
             )
         )
@@ -620,6 +635,7 @@ def test_android_notification(self):
                     'default_light_settings': False,
                     'visibility': 'PUBLIC',
                     'notification_count': 1,
+                    'proxy': 'IF_PRIORITY_LOWERED'
                 },
             },
         }