Fixes error 400 responses from patched form boundary

[jcd000]

Requests_cache version 1.2.0 causes our server to respond with error 400 on multipart requests.

After some investigation, i tracked this down to PR #919:
With the older format i get a proper response (status 200): FORM_BOUNDARY = '##requests-cache-form-boundary##'
With the new format i get error 400: FORM_BOUNDARY = '==requests-cache-form-boundary=='

I'm not very experienced with requests, but to my understanding RFC2046 suggests "The boundary delimiter line is then defined as a line consisting entirely of two hyphen characters ("-", decimal value 45) [...]"

So, i tested replacing the "==" with hyphens "--" in the below formats:

1. FORM_BOUNDARY = '--requests-cache-form-boundary--'
2. FORM_BOUNDARY = '--requests-cache-form-boundary'

Both formats above seem to be accepted with no problems.

Unless i am missing something, I would propose to keep the 1st format, which seems more in line with the past forms.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.37%. Comparing base (167e852) to head (be91e87).
Report is 5 commits behind head on main.

Additional details and impacted files

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  Coverage   99.37%   99.37%           
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  Files          23       23           
  Lines        1908     1908           
  Branches      337      338    +1     
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  Hits         1896     1896           
  Misses          5        5           
  Partials        7        7           

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[JWCook]

Thanks for contributing a fix for this.

For others' reference, do you have more details on what caused your server to not process a form boundary starting with ==?

[jcd000]

Thanks for contributing a fix for this.

For others' reference, do you have more details on what caused your server to not process a form boundary starting with ==?

Thanks for accepting the PR.
I'm sorry i can't help more with debugging the root cause: I can't access server backend / logs.
Maybe helpful: in the response headers i can see: x-oracle-dms-rid: 0:4, which points to Oracle Identity Cloud Service.