Readme for cloud sql module

modules/cloud-sql/README.md

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+# Cloud SQL Module
+
+This module creates a [Google Cloud SQL](https://cloud.google.com/sql/) cluster. The cluster is managed by Google, 
+automating backups, replication, patches, and updates. 
+
+You can use Cloud SQL with either [MySQL](https://cloud.google.com/sql/docs/mysql/) or [PostgreSQL](https://cloud.google.com/sql/docs/postgres/).
+
+## How do you use this module?
+
+See the [examples](/examples) folder for an example. 
+
+## How do you connect to the database?
+
+This module provides the connection details as [Terraform output 
+variables](https://www.terraform.io/intro/getting-started/outputs.html):
+
+1. **Cluster endpoint**: The endpoint for the whole cluster. You should always use this URL for writes, as it points to 
+   the primary.
+1. **Instance endpoints**: A comma-separated list of all DB instance URLs in the cluster, including the primary and all
+   read replicas. Use these URLs for reads (see "How do you scale this DB?" below).
+1. **Port**: The port to use to connect to the endpoints above.
+
+TODO: Connectivity and output
+
+For more info, see [Connecting to Cloud SQL from External Applications](https://cloud.google.com/sql/docs/mysql/connect-external-app).
+
+You can programmatically extract these variables in your Terraform templates and pass them to other resources (e.g. 
+pass them to User Data in your EC2 instances). You'll also see the variables at the end of each `terraform apply` call 
+or if you run `terraform output`.
+
+## How do you scale this database?
+
+* **Storage**: Cloud SQL manages storage for you, automatically growing cluster volume up to 10TB.
+* **Vertical scaling**: To scale vertically (i.e. bigger DB instances with more CPU and RAM), use the `machine_type` 
+  input variable. For a list of Cloud SQL Machine Types, see [Cloud SQL Pricing](https://cloud.google.com/sql/pricing#2nd-gen-pricing).
+* **Horizontal scaling**: To scale horizontally, you can add more replicas using the `instance_count` input variable, 
+  and Aurora will automatically deploy the new instances, sync them to the master, and make them available as read 
+  replicas.
+
+## How do you configure this module?
+
+This module allows you to configure a number of parameters, such as backup windows, maintenance window, port number,
+and encryption. For a list of all available variables and their descriptions, see [variables.tf](./variables.tf).
+
+## Known Issues
+
+### Instance Recovery
+
+Due to limitations on the current `terraform` provider for Google, it is not possible to restore backups with `terraform`. 
+See https://github.com/terraform-providers/terraform-provider-google/issues/2446
+
+