develop.sh: attempt to create a Docker template automatically (#2627)

This commit makes the following changes:

- Adds two variables docker_host and docker_arch to the example docker-code-server template
- Adds an example params.yaml to docker-code-server and updates the README.md to reference these parameters
- scripts/develop.sh will now attempt to create a template using docker-code-server with the appropriate parameters for the environment
- Updated Lima example to make use of the template parameters for docker-code-server


Additional drive-bys:

- webpack.dev.ts references CODER_HOST and not CODERV2_HOST; updated develop.sh accordingly
- develop.sh should now terminate child processes upon error.

examples/templates/docker-code-server/README.md

@@ -8,4 +8,18 @@ tags: [local, docker]
 
 ## Getting started
 
-Run `coder templates init` and select this template. Follow the instructions that appear. 
+Run `coder templates init` and select this template. Follow the instructions that appear.
+
+## Supported Parameters
+
+You can create a file containing parameters and pass the argument
+`--parameter-file` to `coder templates create`.
+See `params.sample.yaml` for more information.
+
+This template has the following predefined parameters:
+
+- `docker_host`: Path to (or address of) the Docker socket.
+  > You can determine the correct value for this by runnning
+  > `docker context ls`.
+- `docker_arch`: Architecture of the host running Docker.
+  This can be `amd64`, `arm64`, or `armv7`.

examples/templates/docker-code-server/main.tf

@@ -11,14 +11,32 @@ terraform {
   }
 }
 
+variable "docker_host" {
+  description = "Specify location of Docker socket (check `docker context ls` if you're not sure)"
+  sensitive   = true
+}
+
+variable "docker_arch" {
+  description = "Specify architecture of docker host (amd64, arm64, or armv7)"
+  validation {
+    condition     = contains(["amd64", "arm64", "armv7"], var.docker_arch)
+    error_message = "Value must be amd64, arm64, or armv7."
+  }
+  sensitive = true
+}
+
 provider "coder" {
 }
 
+provider "docker" {
+  host = var.docker_host
+}
+
 data "coder_workspace" "me" {
 }
 
 resource "coder_agent" "dev" {
-  arch           = "amd64"
+  arch           = var.docker_arch
   os             = "linux"
   startup_script = "code-server --auth none"
 }

examples/templates/docker-code-server/params.sample.yaml

@@ -0,0 +1,2 @@
+docker_host: "unix:///var/run/docker.sock"
+docker_arch: "amd64"