Add support for templates on broadcasts part 1

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.47826% with 3 lines in your changes missing coverage. Please review.

Project coverage is 62.82%. Comparing base (4eb83e1) to head (dd289b1).

Files	Patch %	Lines
core/models/templates.go	76.92%	2 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #277 +/- ## ========================================== + Coverage 62.80% 62.82% +0.02% ========================================== Files 187 187 Lines 10428 10439 +11 ========================================== + Hits 6549 6558 +9 - Misses 3008 3010 +2 Partials 871 871 ```

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