docs: add section for how to handle update servers with auth (#23000)
docs: add section for how to handle update servers with auth (#23000)

In some situations, we can't use auto update to communicate with our update server directly, and proxies can be tricky to get working. I spent a loooong time exploring a lot of options before coming across the comment I linked, so It thought it could be beneficial to people like me of the future.
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