feat: convert datasource to resource (#15)

- Convert datasource to resource
- Update examples
- Update tests

examples/data-sources/envbuilder_cached_image/data-source.tf

@@ -1,13 +0,0 @@
-data "envbuilder_cached_image" "example" {
-  builder_image = "ghcr.io/coder/envbuilder:latest"
-  git_url       = "https://github.com/coder/envbuilder-starter-devcontainer"
-  cache_repo    = "localhost:5000/local/test-cache"
-  extra_env = {
-    "ENVBUILDER_VERBOSE" : "true"
-  }
-}
-
-resource "docker_container" "container" {
-  image = envbuilder_cached_image.example.image
-  env   = data.envbuilder_image.cached.env
-}

examples/resources/envbuilder_cached_image/envbuilder_cached_image_resource.tf

@@ -0,0 +1,93 @@
+// The below example illustrates the behavior of the envbuilder_cached_image
+// resource.
+// 1) Run a local registry:
+// 
+//    ```shell
+//    docker run -d -p 5000:5000 --name test-registry registry:2
+//    ```
+//
+// 2) Running a `terraform plan` should result in the following outputs:
+// 
+//    ```
+//    + builder_image = "ghcr.io/coder/envbuilder-preview:latest"
+//    + exists        = (known after apply)
+//    + id            = (known after apply)
+//    + image         = (known after apply)
+//    ```
+//
+// 3) Running `terraform apply` should result in outputs similar to the below:
+// 
+//    ```
+//       builder_image = "ghcr.io/coder/envbuilder-preview:latest"
+//       exists = false
+//       id = "00000000-0000-0000-0000-000000000000"
+//       image = "ghcr.io/coder/envbuilder-preview:latest"
+//    ```
+//
+// 4) Populate the cache by running Envbuilder and pushing the built image to
+//    the local registry:
+//
+//    ```shell
+//       docker run -it --rm \
+//         -e ENVBUILDER_CACHE_REPO=localhost:5000/test \
+//         -e ENVBUILDER_GIT_URL=https://github.com/coder/envbuilder-starter-devcontainer \
+//         -e ENVBUILDER_PUSH_IMAGE=true \
+//         -e ENVBUILDER_INIT_SCRIPT=exit \
+//         --net=host \
+//         ghcr.io/coder/envbuilder-preview:latest
+//    ```
+//
+// 5) Run `terraform plan` once more. Now, the cached image will be detected:
+//
+//    ```
+//       Note: Objects have changed outside of Terraform
+//
+//       Terraform detected the following changes made outside of Terraform since the last "terraform apply" which may have affected this plan:
+//        envbuilder_cached_image.example has been deleted
+//         - resource "envbuilder_cached_image" "example" {
+//         - exists        = false -> null
+//         - id            = "00000000-0000-0000-0000-000000000000" -> null
+//         - image         = "ghcr.io/coder/envbuilder-preview:latest" -> null
+//           # (5 unchanged attributes hidden)
+//    ```
+//
+//    6) Run `terraform apply` and the newly pushed image will be saved in the Terraform state:
+//    ```shell
+//       builder_image = "ghcr.io/coder/envbuilder-preview:latest"
+//       exists = true
+//       id = "sha256:xxx..."
+//       image = "localhost:5000/test@sha256:xxx..."
+//    ```
+
+terraform {
+  required_providers {
+    envbuilder = {
+      source = "coder/envbuilder"
+    }
+  }
+}
+
+resource "envbuilder_cached_image" "example" {
+  builder_image = "ghcr.io/coder/envbuilder-preview:latest"
+  git_url       = "https://github.com/coder/envbuilder-starter-devcontainer"
+  cache_repo    = "localhost:5000/test"
+  extra_env = {
+    "ENVBUILDER_VERBOSE" : "true"
+  }
+}
+
+output "builder_image" {
+  value = envbuilder_cached_image.example.builder_image
+}
+
+output "exists" {
+  value = envbuilder_cached_image.example.exists
+}
+
+output "id" {
+  value = envbuilder_cached_image.example.id
+}
+
+output "image" {
+  value = envbuilder_cached_image.example.image
+}