AwsVpcPeering prevent CIDR overlapping of the remote and pods network

[ijovovic]

Problem
If the peered remote VPC CIDR overlaps with the Kymas Kubernetes pods network, Kyma workloads want be able to hit services in remote network.

For example lets have the folllowing Kyma network configuration

networking:
pods: 10.96.0.0/13
nodes: 10.250.0.0/22
services: 100.104.0.0/13
And remote network CIDR 10.100.0.0/17 that overlaps with pods CIDR 10.96.0.0/13.

After applying the AwsVpcPeering resources Cloud Manager will establish VPC peering connection since the CIDRs of the physical networks beeing peered does not collide.

AWS VPC peering API is not aware of the configured pods and services container networks therefore it does not take them into account.

Proposed solution
We must document this limitation so that users does not run into an issue while configuring their networking.

Check whether remote VPC CIDR overlaps with the Kymas Kubernetes pods network before VPC peering connection is established and show a Warning to the user.