🧛 Populate ticket_count when creating new contacts

[rowanseymour]

Requires nyaruka/rapidpro#3461 by deployed first

Also fixes tests broken by recent db changes to msgs and broadcasts.

[codecov]

Codecov Report

Merging #467 (39eb79d) into main (9f4fa51) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #467   +/-   ##
=======================================
  Coverage   56.99%   56.99%           
=======================================
  Files         123      123           
  Lines        8598     8598           
=======================================
  Hits         4900     4900           
  Misses       2921     2921           
  Partials      777      777           

Impacted Files	Coverage Δ
core/models/msgs.go	51.09% <ø> (ø)
core/models/contacts.go	62.61% <100.00%> (ø)

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