AKS/EKS core fluxcd v2 type validation

[simongottschlag]

We are not validating the type variable for flux v2:

terraform-modules/modules/kubernetes/aks-core/variables.tf

Line 128 in ed7a12c

type = string

Possible configurations are azure-devops and github:

terraform-modules/modules/kubernetes/aks-core/modules.tf

Line 97 in ed7a12c

if var.fluxcd_v2_enabled && var.fluxcd_v2_config.type == "azure-devops"

terraform-modules/modules/kubernetes/aks-core/modules.tf

Line 123 in ed7a12c

if var.fluxcd_v2_enabled && var.fluxcd_v2_config.type == "github"

We should create a validation for the fluxcd_v2_config variable that validates that it's one of those.