Do more error wrapping when creating contacts and URNs

[rowanseymour]

So we can see where the context canceled errors are coming from

[codecov]

Codecov Report

Merging #396 (db8727b) into main (3163cff) will increase coverage by 0.00%.
The diff coverage is 6.25%.

@@           Coverage Diff           @@
##             main     #396   +/-   ##
=======================================
  Coverage   71.70%   71.71%           
=======================================
  Files          95       95           
  Lines        8257     8256    -1     
=======================================
  Hits         5921     5921           
+ Misses       1747     1746    -1     
  Partials      589      589           

Impacted Files	Coverage Δ
backends/rapidpro/contact.go	46.75% <0.00%> (+0.59%)	⬆️
backends/rapidpro/msg.go	68.39% <0.00%> (ø)
backends/rapidpro/urn.go	72.32% <25.00%> (ø)

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