add implicit inverse foreign keys when necessary

[erizocosmico]

No description provided.

[codecov]

Codecov Report

Merging #177 into master will decrease coverage by 0.03%.
The diff coverage is 78.57%.

@@            Coverage Diff            @@
##           master    #177      +/-   ##
=========================================
- Coverage   81.23%   81.2%   -0.04%     
=========================================
  Files          16      16              
  Lines        3443    3485      +42     
=========================================
+ Hits         2797    2830      +33     
- Misses        439     444       +5     
- Partials      207     211       +4

Impacted Files	Coverage Δ
generator/processor.go	88.73% <0%> (-0.63%)	⬇️
generator/template.go	92.83% <100%> (+0.15%)	⬆️
generator/types.go	85.99% <78.12%> (-0.66%)	⬇️

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