add missing DRU conformance/requirement references

[fmigneault]

• add missing DRU conformance requirements (fixes Conformance definitions for /processes/{process_id}/package endpoint #620)
• fix unsuported-content-type for invalid deploy/update (fixes Indicate unsupported-content-type in POST process response #624)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.08%. Comparing base (8416019) to head (034842a).
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #740      +/-   ##
==========================================
- Coverage   86.08%   86.08%   -0.01%     
==========================================
  Files          80       80              
  Lines       19577    19577              
  Branches     2629     2629              
==========================================
- Hits        16853    16852       -1     
  Misses       1983     1983              
- Partials      741      742       +1     

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