Rework more mailroom client methods

[rowanseymour]

No description provided.

[sentry-io]

🔍 Existing Issues For Review

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

📄 File: temba/msgs/models.py

Function	Unhandled Issue
create	RequestException: error inserting broadcast: error inserting contacts for broadcast: error making bulk query: error... ... Event Count: 5

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (2da1bfb) to head (6f36a2d).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #5316   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          483       483           
  Lines        25042     25030   -12     
=========================================
- Hits         25042     25030   -12     

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