Add browser IDC authentication method

[VersusFacit]

partially completes #898

Problem

We want to add additional authentication methods using IAM Identity Center for Redshift.

Solution

This Pull request completes one requirement by adding the browser-based authentication method.

I've refactored the code to be purely functional and assemble parameters in a tail-recursive fashion so the code reflects a gradual build up of reusable chunks.

Along with this PR is a lot of research and experimentation in Redshift/Iam to get a model to build on Redshift using this method!

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-redshift contributing guide.

[VersusFacit]

I figured out the browser setup 🚀 Can't be automated really but this along with the unit tests tells me the browser method is good to go engineering wise. We are waiting on some product experience review notes from Amy though.

[VersusFacit]

Latest pushed sha re-confirmed builds a model correctly 👍

[mikealfare]

A few suggestions, nothing blocking. I like the refactor to a more functional approach.

[VersusFacit]

@cla-bot check

[mikealfare]

CLA-bot is not working at the moment. The PR author is a dbt Labs employee, hence has signed the CLA. Merging with manual verification.