feat(proxy): stream request body with streamRequest option

[iainsproat]

Example of problem and roughly-sketched implementation for #373

This PR amends the behaviour of proxyRequest to stream the proxied request to the upstream target.

Note that this PR is a rough hack and doesn't represent a polished solution.

[codecov]

Codecov Report

Merging #374 (a6e8c65) into main (78aec63) will increase coverage by 0.00%.
The diff coverage is 84.61%.

@@           Coverage Diff           @@
##             main     #374   +/-   ##
=======================================
  Coverage   78.37%   78.38%           
=======================================
  Files          26       26           
  Lines        2793     2803   +10     
  Branches      407      408    +1     
=======================================
+ Hits         2189     2197    +8     
- Misses        604      606    +2     

Files Changed	Coverage Δ
src/utils/proxy.ts	81.44% <84.61%> (-0.07%)	⬇️

[pi0]

Thanks for the nice PR! With recently introduced (experimental) event.body that returns a readable stream. Based on this, i think introducing this enhancement at least behind an option flag (streamRequest) would be a nice idea. I have made some refactors to do this.

[iainsproat]

Thanks for picking this up @pi0 - great work in adding the missing parts and getting it over the line! I'm looking forward to using this very soon :)