Adding pkce support field

[uhunnyslack]

Summary

To support more connectors, 3p auth manifest config requires some more new SDK fields

This PR is to add a new field that helps the connector team unblock creating some more connectors.

use_pkce : boolean -> this is true for providers that uses PKCE:

More discussions can be found in our slack instance.

Important

Please do not merge it until the web app changes are merged! Thanks!

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 #203 (32e7e97) into main (f7b4a35) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #203   +/-   ##
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  Coverage   99.24%   99.24%           
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  Files          56       56           
  Lines        2128     2128           
  Branches      136      136           
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  Hits         2112     2112           
  Misses         15       15           
  Partials        1        1           

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[filmaj]

@uhunnyslack I've assigned this PR to you and added the do not merge label to it. Feel free to merge whenever you are ready.