fix: give preference to the oldKey of the user options and use the default as the fallback

[laksh-twilio]

https://twilio-engineering.atlassian.net/browse/LIBRARIES-2775

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⚠️ No Changeset found

Latest commit: d76551b

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.56%. Comparing base (0555f07) to head (d76551b).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1363      +/-   ##
==========================================
- Coverage   91.72%   90.56%   -1.16%     
==========================================
  Files         163       82      -81     
  Lines        4674     1907    -2767     
  Branches     1155      444     -711     
==========================================
- Hits         4287     1727    -2560     
+ Misses        387      180     -207     

Flag	Coverage Δ
browser	?
core	90.07% <ø> (ø)
node	90.36% <ø> (ø)

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