Add extra_credentials to clickhouse destination configuration

[warje]

Description

Adds a new configuration option to the clickhouse destination named extra_credentials which will map to the extra_credentials argument to the s3 function. This allows dlt to use role based authentication in alignment with the clickhouse docs

Related Issues

• Fixes #2887

Additional Context

Currently using this change in our staging and production environments.

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[warje]

Hey, thanks for this PR :) I have one note about the naming of the setting and two requests:

* Please add a simple test where you check the building of these strings depending on different settings

* Please update the clickhouse docs page and include information about this new setting

Thank you for the review and for your work on the project.

I have made the requested changes which includes tests and doc updates.

Regarding the unit tests. I refactored the run method a little to make it easier to test this specific change without running a pipeline.

I gave the unit tests a good shot, but honestly got a little confused with the test project structure specifically in the loads directory so if you have advise or guidance as far as what I can do differently, I would appreciate to hear it.