feat: Make backend proxy algorithm configurable

[bnevis-i]

Allow backend proxy to be automatic, direct, or api-gateway. Needed for Kubernetes deployment in secure mode

Closes #635

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PR Checklist

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• I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• I am not introducing a new dependency (add notes below if you are)
• I have added unit tests for the new feature or bug fix (if not, why?)
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Testing Instructions

Have only tested this in kubernetes. Needs a docker regression as well.

New Dependency Instructions (If applicable)