Add Serde.default_value for request_options

[IlyaVshivtsev]

Pull request checklist

• Did you bump the project version?
• Did you add a description to the Pull Request?
• Did you add new tests?
• Did you add reviewers?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/v0.35.0@08322cb). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/Aevo/Aevo.jl	0.00%	1 Missing ⚠️
src/Binance/Binance.jl	0.00%	1 Missing ⚠️
src/Bitfinex/Bitfinex.jl	0.00%	1 Missing ⚠️
src/Bithumb/Bithumb.jl	0.00%	1 Missing ⚠️
src/Bybit/Bybit.jl	0.00%	1 Missing ⚠️
src/Coinbase/Coinbase.jl	0.00%	1 Missing ⚠️
src/Cryptocom/Cryptocom.jl	0.00%	1 Missing ⚠️
src/Deribit/Deribit.jl	0.00%	1 Missing ⚠️
src/Gateio/Gateio.jl	0.00%	1 Missing ⚠️
src/Huobi/Huobi.jl	0.00%	1 Missing ⚠️
... and 6 more

Additional details and impacted files

@@                Coverage Diff                @@
##             release/v0.35.0     #81   +/-   ##
=================================================
  Coverage                   ?   3.99%           
=================================================
  Files                      ?     253           
  Lines                      ?    2601           
  Branches                   ?       0           
=================================================
  Hits                       ?     104           
  Misses                     ?    2497           
  Partials                   ?       0           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.