Set sent_on for outgoing IVR messages

[rowanseymour]

No description provided.

[codecov]

Codecov Report

Merging #463 (d967560) into main (8de59cb) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #463      +/-   ##
==========================================
- Coverage   56.60%   56.59%   -0.01%     
==========================================
  Files         123      123              
  Lines        8593     8594       +1     
==========================================
  Hits         4864     4864              
- Misses       2952     2953       +1     
  Partials      777      777              

Impacted Files	Coverage Δ
core/models/msgs.go	45.61% <0.00%> (-0.11%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8de59cb...d967560. Read the comment docs.