service principal support

[davidgamero]

Description

Add the ability to authenticate using service principals instead of MSI

Fixes # (issue) Feature # (details)

Type of change

Please delete options that are not relevant.

• [X] New feature (non-breaking change which adds functionality)
• [X] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration. Is it a breaking change which will impact consuming tool(s)?

• [X] Added new e2e infra service principal to the matrix, validating every existing e2e test on the new configuration
• [X] Added new unit tests

Checklist:

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

[coveralls]

Pull Request Test Coverage Report for Build 6592562485

• 61 of 78 (78.21%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.6%) to 88.286%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/controller/keyvault/placeholder_pod.go	12	16	75.0%
pkg/manifests/external_dns.go	33	46	71.74%
<!--	Total:	61	78	78.21%	-->

Totals
Change from base Build 6549676137:	-0.6%
Covered Lines:	2050
Relevant Lines:	2322

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💛 - Coveralls

[OliverMKing]

Going to close for now since we've opted not to add sp support. Likely will implement sp support through workload identity in the future