add datadog django integration (ddtrace)

[danlipert]

Description

This PR adds the datadog django integration (ddtrace)

Refers/Fixes

n/a

Testing

untested but env flagged

[codecov]

Codecov Report

Merging #5847 into master will increase coverage by <.01%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master    #5847      +/-   ##
==========================================
+ Coverage   29.55%   29.55%   +<.01%     
==========================================
  Files         266      266              
  Lines       22653    22656       +3     
  Branches     3289     3290       +1     
==========================================
+ Hits         6694     6695       +1     
+ Misses      15682    15680       -2     
- Partials      277      281       +4

Impacted Files	Coverage Δ
app/app/settings.py	80.06% <33.33%> (-0.48%)	⬇️
app/dashboard/views.py	11.63% <0%> (ø)	⬆️
...rketing/management/commands/no_applicants_email.py	0% <0%> (ø)	⬆️

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