bugfix - force ProductCategory Code to be unique

[jsirish]

fixes #339

[codecov]

Codecov Report

Merging #371 into master will decrease coverage by 0.07%.
The diff coverage is 16.66%.

@@             Coverage Diff              @@
##             master     #371      +/-   ##
============================================
- Coverage     29.04%   28.97%   -0.08%     
- Complexity      437      439       +2     
============================================
  Files            28       28              
  Lines          1821     1826       +5     
============================================
  Hits            529      529              
- Misses         1292     1297       +5

Impacted Files	Coverage Δ	Complexity Δ
src/Model/ProductCategory.php	85.84% <16.66%> (-3.98%)	22 <2> (+2)

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[codecov]

Codecov Report

Merging #371 into master will decrease coverage by 0.07%.
The diff coverage is 16.66%.

@@             Coverage Diff              @@
##             master     #371      +/-   ##
============================================
- Coverage     29.04%   28.97%   -0.08%     
- Complexity      437      439       +2     
============================================
  Files            28       28              
  Lines          1821     1826       +5     
============================================
  Hits            529      529              
- Misses         1292     1297       +5

Impacted Files	Coverage Δ	Complexity Δ
src/Model/ProductCategory.php	85.84% <16.66%> (-3.98%)	22 <2> (+2)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8cd82bd...a8025f4. Read the comment docs.