fix: serialized responses containing a self-join is missing attributes

[zacharygolba]

This PR fixes a bug where attributes of a model are not included in serialized responses if the model has a self-join in the form of a n:m relationship. Closes #607.

See the follower/followee relationship in the social network example.

[codecov-io]

Codecov Report

Merging #675 into master will increase coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #675      +/-   ##
==========================================
+ Coverage    92.3%   92.38%   +0.08%     
==========================================
  Files         180      180              
  Lines        2000     1996       -4     
==========================================
- Hits         1846     1844       -2     
+ Misses        154      152       -2

Impacted Files	Coverage Δ
...oute/params/utils/get-default-collection-params.js	100% <ø> (+20%)	✅
...er/route/params/utils/get-default-member-params.js	100% <100%> (+20%)	✅

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