Add Urgent Notif (iOS)

[vcai122]

ex:
{'aps': {'alert': {'title': 'a', 'body': 'b'}, 'badge': 0, 'sound': 'default', 'mutable-content': 1, 'interruption-level': 'time-sensitive'}}

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: backend/user/notifications.py

Function	Unhandled Issue
send_payload	AttributeError: 'IOSNotificationWrapper' object has no attribute 'client' notifications.... Event Count: 6

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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 10 lines in your changes missing coverage. Please review.

Project coverage is 88.29%. Comparing base (73dc150) to head (e18f4c6).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
backend/user/notifications.py	55.55%	8 Missing ⚠️
backend/user/views.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #333      +/-   ##
==========================================
- Coverage   88.46%   88.29%   -0.18%     
==========================================
  Files          67       67              
  Lines        2766     2776      +10     
==========================================
+ Hits         2447     2451       +4     
- Misses        319      325       +6     

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