docs: update azurerm backend docs

[jaredfholgate]

This PR refactors the documentation for the azurerm backend to provide clarity for users on the various authentication options. The existing documentation was missing clarity on the Access Key vs Entra ID option to access the storage account. This change is designed to provide that clarity and make it clear that the use_azuread_auth variable is not mutually exclusive with the other authentication options, it is additive.

Fixes N/A

Target Release

1.7.1

Draft CHANGELOG entry

NEW FEATURES | UPGRADE NOTES | ENHANCEMENTS | BUG FIXES | EXPERIMENTS

[jaredfholgate]

@luke-taylor Thanks for spotting all my typos! :)

[manicminer]

Hi @jaredledvina, thanks for this PR! I agree that the array of configuration options around authentication, particularly with storage, and even more so in the context of the remote backend, can be very challenging to reason about. I agree that better examples improve the documentation and I like what you're put together here.

I've gone through and tidied up a little, as well as made some suggestions around wording - notably the use of the new branding of Entra ID. We are likely going to update all our docs together at some point, but in the meantime we are continuing to refer to the platform as Azure Active Directory. This is both for consistency, to reduce overall confusion, and to avoid a PR surge where these references are changed piecemeal. I've also tweaked the table of auth scenarios to merge the two rightmost columns.

Since my suggestions are all formatting related, or minor wording changes, I'm going to go ahead and incorporate these and merge your PR. Thanks again for working on this, I expect you have spent a lot of time on this and it's greatly appreciated 🚀

[jaredfholgate]

@manicminer LGTM, thanks for the updates.

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