Move search into its own package and add more tests

[rowanseymour]

No description provided.

[codecov]

Codecov Report

Merging #620 (241c617) into main (3314713) will decrease coverage by 0.90%.
The diff coverage is 77.85%.

@@            Coverage Diff             @@
##             main     #620      +/-   ##
==========================================
- Coverage   62.88%   61.98%   -0.91%     
==========================================
  Files         128      130       +2     
  Lines       12840    12848       +8     
==========================================
- Hits         8075     7964     -111     
- Misses       3890     4029     +139     
+ Partials      875      855      -20     

Impacted Files	Coverage Δ
core/models/groups.go	23.25% <ø> (-37.67%)	⬇️
core/tasks/contacts/populate_dynamic_group.go	62.50% <60.00%> (ø)
core/search/groups.go	63.63% <63.63%> (ø)
core/search/search.go	70.33% <83.33%> (ø)
core/search/queries.go	94.23% <94.23%> (ø)
core/tasks/starts/worker.go	53.89% <100.00%> (ø)
web/contact/search.go	78.02% <100.00%> (ø)
web/flow/start.go	62.50% <100.00%> (-24.27%)	⬇️
core/models/campaigns.go	33.78% <0.00%> (-15.21%)	⬇️
... and 1 more

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