Extauth aerospike apikey storage

[jbohanon]

Description

PoC implementation of generalizing API for ExtAuth API keys in order to allow for Aerospike implementation of storage backend in ExtAuth in lieu of k8s secrets. This will also take the opinionated approach of centralizing management of API Keys within ExtAuth, and as such there is a simple CRUD RPC API defined.

Context

A customer is looking to use multiple k8s clusters running the same application workloads in Active-Active HA configuration, and they will need stateful data stored outside of the cluster so it is preserved in the event of failover. They wish to use an existing Aerospike deployment in their infrastructure to house the stateful data.

Checklist:

• [ ] I included a concise, user-facing changelog (for details, see https://github.com/solo-io/go-utils/tree/master/changelogutils) which references the issue that is resolved.
• [ ] If I updated APIs (our protos) or helm values, I ran make -B install-go-tools generated-code to ensure there will be no code diff
• [ ] I followed guidelines laid out in the Gloo Edge contribution guide
• [ ] I opened a draft PR or added the work in progress label if my PR is not ready for review
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works