feat(api): include tokens in approval transactions

[oXtxNt9U]

Summary

#1236 added the tokens field to transactions when tokens are transferred.

This PR extends it to also cover approval transactions.

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.60%. Comparing base (feefb65) to head (6f7844f).

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #1239       +/-   ##
============================================
+ Coverage    53.09%   98.60%   +45.50%     
============================================
  Files         1121        3     -1118     
  Lines        62313      430    -61883     
  Branches      1700       77     -1623     
============================================
- Hits         33088      424    -32664     
+ Misses       29070        4    -29066     
+ Partials       155        2      -153     

Flag	Coverage Δ
contracts	98.60% <ø> (?)
packages	?

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