Add new trigger_session action to replace start_session

[rowanseymour]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 55.35714% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.80%. Comparing base (f5d91b4) to head (da76c4e).
⚠️ Report is 735 commits behind head on main.

Files with missing lines	Patch %	Lines
flows/actions/trigger_session.go	64.44%	11 Missing and 5 partials ⚠️
flows/events/session_triggered.go	10.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1288      +/-   ##
==========================================
- Coverage   81.89%   81.80%   -0.09%     
==========================================
  Files         276      277       +1     
  Lines       17460    17514      +54     
==========================================
+ Hits        14298    14327      +29     
- Misses       2590     2610      +20     
- Partials      572      577       +5     

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