generate/hcl: support module calls through source keyword

[tormath1]

In this PR, we add the support for module calls. It supports local, remote and Terraform registry ones.

The function moduleInstall is called recursively in order to walk through the ModuleCalls of each module to feed a ManagedResource slice. It stores a trace of each installed element to avoid infinite loops and modules are cached into $XDG_CACHE directory.

Then it loops over the ManagedResource slice with the current behavior.

A few notes:

1. I'd like to use in-memory FS rather than actual FS but go-getter needs to be updated consequently (Abstract the os access via interface hashicorp/go-getter#83: I started to work on it btw)
2. I still need to find a way to properly testing this :)

Output example using this stack: https://github.com/cycloid-community-catalog/stack-gke

$ ./inframap generate --hcl generate/testdata/stack-gke
strict digraph G {
        "google_container_node_pool.pools"->"google_container_cluster.primary";
        "null_resource.delete_default_kube_dns_configmap"->"google_container_cluster.primary";
        "null_resource.delete_default_kube_dns_configmap"->"google_container_node_pool.pools";
        "kubernetes_config_map.kube-dns-upstream-namservers"->"null_resource.delete_default_kube_dns_configmap";
        "kubernetes_config_map.kube-dns-upstream-namservers"->"google_container_cluster.primary";
        "kubernetes_config_map.kube-dns-upstream-namservers"->"google_container_node_pool.pools";
        "kubernetes_config_map.kube-dns-upstream-nameservers-and-stub-domains"->"null_resource.delete_default_kube_dns_configmap";
        "kubernetes_config_map.kube-dns-upstream-nameservers-and-stub-domains"->"google_container_cluster.primary";
        "kubernetes_config_map.kube-dns-upstream-nameservers-and-stub-domains"->"google_container_node_pool.pools";
        "kubernetes_config_map.ip-masq-agent"->"google_container_cluster.primary";
        "kubernetes_config_map.ip-masq-agent"->"google_container_node_pool.pools";
        "null_resource.wait_for_cluster"->"google_container_cluster.primary";
        "null_resource.wait_for_cluster"->"google_container_node_pool.pools";
        "google_service_account.cluster_service_account"->"random_string.cluster_service_account_suffix";
        "kubernetes_config_map.kube-dns"->"null_resource.delete_default_kube_dns_configmap";
        "kubernetes_config_map.kube-dns"->"google_container_cluster.primary";
        "kubernetes_config_map.kube-dns"->"google_container_node_pool.pools";
        "google_container_cluster.primary" [ shape=ellipse ];
        "google_container_node_pool.pools" [ shape=ellipse ];
        "google_service_account.cluster_service_account" [ shape=ellipse ];
        "kubernetes_config_map.ip-masq-agent" [ shape=ellipse ];
        "kubernetes_config_map.kube-dns" [ shape=ellipse ];
        "kubernetes_config_map.kube-dns-upstream-nameservers-and-stub-domains" [ shape=ellipse ];
        "kubernetes_config_map.kube-dns-upstream-namservers" [ shape=ellipse ];
        "null_resource.delete_default_kube_dns_configmap" [ shape=ellipse ];
        "null_resource.wait_for_cluster" [ shape=ellipse ];
        "random_string.cluster_service_account_suffix" [ shape=ellipse ];

}

[tibeer]

This change looks fine to me. May I ask why there hasn't been any progress on this?

[tormath1]

hi @tibeer , progress was stopped because go-getter still does not support in-memory FS. We could try to merge it in this current state then. I opened a new PR (#130) because I changed change my source branch from this repo to my fork, rebase has been done too. cc @xescugc