GH-475: Prevent sending empty payloads for client addons

[sergiught]

🔧 Changes

This fixes an issue where we would send an empty payload for all the client addons, even if modifying or adding just one type.

📚 References

🔬 Testing

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

[codecov-commenter]

Codecov Report

Merging #759 (ac56355) into v1 (48b575c) will increase coverage by 0.60%.
The diff coverage is 96.42%.

Additional details and impacted files

@@            Coverage Diff             @@
##               v1     #759      +/-   ##
==========================================
+ Coverage   89.80%   90.41%   +0.60%     
==========================================
  Files          99       99              
  Lines       13077    13119      +42     
==========================================
+ Hits        11744    11861     +117     
+ Misses        941      891      -50     
+ Partials      392      367      -25     

Files Changed	Coverage Δ
internal/auth0/client/resource.go	98.84% <62.50%> (-0.25%)	⬇️
internal/auth0/client/expand.go	91.75% <100.00%> (+3.58%)	⬆️
internal/auth0/client/flatten.go	98.69% <100.00%> (+13.23%)	⬆️