Use GitLab serverless with existing Knative installation

Problem to solve

Currently, the serverless features is enabled when a knative deployment via GitLab k8s integration is detected, however, if I bring an existing cluster that already has knative deployed to it, I cannot take advantage of all the great features of GitLab serverless.

Further details

Proposal

When an existing cluster is added, detect the presence of Knative and enable cluster to be used with all the existing features of GitLab serverless.

Considerations:

1. Will need to detect knative installation (perhaps look for knative-serving namespace)
2. Will need to detect istio installation (istio-subsystem namespace)
3. Will need to detect domain name if any
4. Will need to offer the ability to input domain name if one does not exist

Ability to add or change domain will mimic current UI/UX:

Permissions and Security

Documentation

What does success look like, and how can we measure that?

Links / references