Add docs for granular agent permissions

[eddymoulton]

Adds first docs for granular agent permissions feature.

short links:
https://oc.to/octopus-permissions-controller: https://octopus.com/docs/kubernetes/targets/kubernetes-agent/granular-permissions
https://oc.to/GranularAgentPermissions: https://octopus.com/docs/kubernetes/targets/kubernetes-agent/granular-permissions
https://oc.to/GranularAgentPermissionsExamples: https://github.com/OctopusDeploy/octopus-permissions-controller/tree/main/examples

[octonautcal]

do we need more troubleshooting scenarios such as "ServiceAccount not being created", "My deployment is using default permissions instead of my WSA" or is that up to us to help them with ?

[eddymoulton]

I am always hesitant to add too many troubleshooting sections early on until I've seen/got reports of problems.
Trying to preempt the problems makes it easy to provide docs that kind of make sense, but don't actually help fix the issue.

Docs are so low cost to add to, so we'll just add more as we go I think.

[octonautcal]

should we include :

    tenants: [tenant-1]
    steps: [step-1]

as well so that it is clearer ? Since the scope section right after mentions them as part of the list

[eddymoulton]

Yeah, I was tossing up whether adding them makes the sample clearer or more muddy - I don't expect people to use the step scope that much and not everyone will be familar with tenants as a concept. I feel like space/project/environment is the minimum that might have people get that "click" moment and understand what it's about.

I'll canvas the team about it.