Discover based on subscription tags

[simongottschlag]

This PR introduces a way to run discover and menu without having Directory reader role (or permission to read all applications which is required to use them today).

To use this, tags starting with _azad-kube-proxy can be added to the subscriptions that we think the users have access to (having read access to a resource group in the subscription grants you access to read the subscription tags).

Example:

_azad-kube-proxy_dev={"cluster_name":"aks-dev-we","resource":"https://aks-we.dev.foobar.io","proxy_url":"https://aks-we.dev.foobar.io"}
_azad-kube-proxy_qa={"cluster_name":"aks-qa-we","resource":"https://aks-we.qa.foobar.io","proxy_url":"https://aks-we.qa.foobar.io"}
_azad-kube-proxy_prod={"cluster_name":"aks-prod-we","resource":"https://aks-we.prod.foobar.io","proxy_url":"https://aks-we.prod.foobar.io"}

Fixes #155

[coveralls]

Coverage decreased (-2.8%) to 86.781% when pulling 3fb0f9c on discovery-subscription-tags into c108ae3 on main.

[NissesSenap]

LGTM, one minor comment which is a personal preference of mine. I understand if you don't agree.
Thanks for quick action :)

[NissesSenap]

@phillebaba do you have any thoughts on this PR?