Research and implement ingress handling

[riccardomc]

We need a way to expose services outside of the cluster and wire the proper DNS entries to said services. Some implementation details will depend on the actual cloud infrastructure that we will end up using. On the other hand, we need a consistent way to track application usage in order to support the mechanism of:

• Rate limiting - we don't want a few chatty applications to use up all the network, in ingress.
• Bandwidth costs allocation - we will want to offload bandwidth costs to paying users at some point.
• Scale to zero - applications that are unused should be scaled to zero to save resources.

Relevant items:

• Kong or API Gateways in general
• External DNS
• Istio for advanced ingress/egress policies control

In the Free Tier we should have at least a coarse way of limiting incoming/outgoing bandwidth usage, not necessarily per application, in order to avert uncontrollable bandwidth costs.

Not relevant for PoC.

[riccardomc]

Other things to look into:

• https://containo.us/traefik/

Traefik has some very interesting features:

• middlewares allow for reacting to requests and responses from applications. This would be useful to implement scale to zero features.
• Out of the box integration with let's encrypt
• Out of the box rate limiting options