Add preliminary module documentation

README.md

@@ -1,3 +1,84 @@
 # Terraform Modules
 
-Collection of reusable Terraform modules
+These modules allow you to conveniently provision and manage your cloud
+resources on Google Cloud Platform (GCP), manage DNS records, document virtual
+machines, and more.
+
+You can use the modules by referencing them directly from our GitHub repository
+[remerge/terraform-modules](https://github.com/remerge/terraform-modules) in
+your Terraform files. Here's a general example:
+
+```hcl
+module "<module_name>" {
+  source = "github.com/remerge/terraform-modules//<module_path>"
+
+  // Insert necessary variables here
+}
+```
+
+Now let's delve into the individual modules:
+
+## consul/dns
+
+This module sets up a DNS forwarding zone for Consul in Google Cloud.
+
+## domain/delegation
+
+This module allows you to create a public DNS zone for a subdomain delegated
+from `remerge/domains`.
+
+## google/compute
+
+With this module, you can create an instance on Google Compute Engine from a
+template.
+
+## google/compute/container
+
+This module allows you to run a container on Google Compute Engine using
+Container OS.
+
+## google/compute/template
+
+With this module, you can create a default Compute Instance template.
+
+## google/kubernetes
+
+This module allows you to create a private Kubernetes cluster on Google Cloud.
+
+## google/redis
+
+This module enables you to create a Redis instance using Google Cloud
+Memorystore.
+
+## google/sql/database
+
+This module allows you to create a database, user, and password for Google Cloud
+SQL.
+
+## google/sql/postgresql
+
+With this module, you can create a PostgreSQL instance using Google Cloud SQL.
+
+## netbox/cluster
+
+This module helps you document a cluster in Netbox and create a corresponding
+private Google Cloud DNS zone.
+
+## netbox/vm
+
+This module assists you in documenting a virtual machine in Netbox and creating
+a corresponding DNS record in Google Cloud DNS.
+
+## nomad/dns
+
+This module allows you to create apex and wildcard DNS records for Nomad
+clients.
+
+## okta/pam/project
+
+This module lets you create an enrollment token and group assignments for Okta
+Advanced Server Access (ScaleFT).
+
+## sendgrid
+
+With this module, you can create a SendGrid API token for SMTP relay access.