feat(coap-core): define mapping from http status to coap code

[szysas]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 71.79487% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.67%. Comparing base (4a66f35) to head (c1b034c).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...-core/src/main/java/com/mbed/coap/packet/Code.java	71.79%	9 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #127      +/-   ##
============================================
- Coverage     92.87%   92.67%   -0.20%     
- Complexity     2055     2078      +23     
============================================
  Files           135      135              
  Lines          4662     4699      +37     
  Branches        623      627       +4     
============================================
+ Hits           4330     4355      +25     
- Misses          186      195       +9     
- Partials        146      149       +3     

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[akolosov-n]

Standardization is key to building robust, interoperable systems, ...