GH-884: Allow client grant scopes to be sent as an empty array

[sergiught]

🔧 Changes

Allow client grant scopes to be sent as an empty array.

📚 References

• Mismatch between arguments for auth0_client_grant  #884

🔬 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 #888 (036f5b4) into main (8ce6af1) will increase coverage by 0.04%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #888      +/-   ##
==========================================
+ Coverage   89.99%   90.03%   +0.04%     
==========================================
  Files         101      101              
  Lines       13783    13779       -4     
==========================================
+ Hits        12404    12406       +2     
+ Misses        977      973       -4     
+ Partials      402      400       -2     

Files	Coverage Δ
internal/auth0/client/expand.go	91.79% <100.00%> (-0.05%)	⬇️
internal/auth0/client/flatten.go	100.00% <100.00%> (+1.30%)	⬆️