Append original stack when WebClient#apiCall throws

[oleg-codaio]

Summary

When an API call within @slack/web-api fails, the resulting error's stack loses the call context:

Error: An API error occurred: account_inactive
     at Object.platformErrorFromResult (/project/node_modules/@slack/web-api/src/errors.ts:94:5)
     at WebClient.apiCall (/project/node_modules/@slack/web-api/src/WebClient.ts:188:13)
     at runMicrotasks (<anonymous>)
     at processTicksAndRejections (internal/process/task_queues.js:97:5)

This PR appends the original stack leading up to the call so that developers can more easily trace failing calls.

For more details, see https://github.com/slackapi/node-slack-sdk/issues/561#issuecomment-679265974

Requirements (place an x in each [ ])

• [x] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.

[codecov[bot]]

Codecov Report

Merging #1086 into main will increase coverage by 0.02%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1086      +/-   ##
==========================================
+ Coverage   94.34%   94.37%   +0.02%     
==========================================
  Files          12       12              
  Lines         796      800       +4     
  Branches      177      177              
==========================================
+ Hits          751      755       +4     
  Misses         15       15              
  Partials       30       30              

Flag	Coverage Δ
#eventsapi	90.74% <ø> (ø)
#interactivemessages	94.83% <ø> (ø)
#webapi	95.63% <ø> (+0.05%)	:arrow_up:
#webhook	87.50% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/WebClient.ts	94.05% <0.00%> (+0.12%)	:arrow_up:

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[stevengill]

Hey @vaskevich!

Thanks for sending this in.

Ended up commenting on the issue to continue discussion

[jaywhiletwo]

This would really improve the developer experience. Currently, errors thrown by the web client are only referencing the stack as they know it when the promise is being resolved. This means we often cannot determine the source of the error without painstaking debugging and isolation steps.