Encoding + User Agent Options

[codefiesta]

Description

• ⭐️ OAuth code reorganization into separate extensions for improved readability.
• OAuth is now using an .ephemeral urlSession instead of the .default urlSession.
• Added additional provider option that allows for setting the customUserAgent.
• Added additional provider option that allows for explicitly setting the encodeHttpBody option (true by default) that either encodes the query parameters into the http body (using application/x-www-form-urlencoded) or simply sends the query parameters with the request.
• Provided sample oauth configurations for Slack and LinkedIn using the new additional provider options.

Fixes #38

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules