Best practices for inter-microservice authentication on Kubernetes?
What you need is a component that acts as the gateway to the microservices API endpoints. That kind of component belongs to a category of software called "API management" (Wikipedia page) and its usage is not limited to Kubernetes only.
There are many choices of API management software such as listed in the Wikipedia page but my project uses Gravitee and so far we are loving it due to its simple administration UI. Feel free to explore it at https://gravitee.io/.
N.B. I'm not related in any way to Gravitee.io apart from being one of the users (although I did contribute to one PR)
I know I'm late now but if anyone else is looking:Istio has included Multicluster support and it makes the communication painless.
reference: https://istio.io/latest/docs/setup/install/multicluster