feat: convert datasource to resource (#15)

- Convert datasource to resource
- Update examples
- Update tests

Author: johnstcn

docs/data-sources/cached_image.md renamed to docs/resources/cached_image.md

@@ -1,32 +1,16 @@
 ---
 # generated by https://github.com/hashicorp/terraform-plugin-docs
-page_title: "envbuilder_cached_image Data Source - envbuilder"
+page_title: "envbuilder_cached_image Resource - envbuilder"
 subcategory: ""
 description: |-
-  The cached image data source can be used to retrieve a cached image produced by envbuilder. Reading from this data source will clone the specified Git repository, read a Devcontainer specification or Dockerfile, and check for its presence in the provided cache repo.
+  The cached image resource can be used to retrieve a cached image produced by envbuilder. Creating this resource will clone the specified Git repository, read a Devcontainer specification or Dockerfile, and check for its presence in the provided cache repo. If any of the layers of the cached image are missing in the provided cache repo, the image will be considered as missing. A cached image in this state will be recreated until found.
 ---
 
-# envbuilder_cached_image (Data Source)
+# envbuilder_cached_image (Resource)
 
-The cached image data source can be used to retrieve a cached image produced by envbuilder. Reading from this data source will clone the specified Git repository, read a Devcontainer specification or Dockerfile, and check for its presence in the provided cache repo.
+The cached image resource can be used to retrieve a cached image produced by envbuilder. Creating this resource will clone the specified Git repository, read a Devcontainer specification or Dockerfile, and check for its presence in the provided cache repo. If any of the layers of the cached image are missing in the provided cache repo, the image will be considered as missing. A cached image in this state will be recreated until found.
 
-## Example Usage
 
-```terraform
-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
-}
-```
 
 <!-- schema generated by tfplugindocs -->
 ## Schema
@@ -63,7 +47,7 @@ resource "docker_container" "container" {
 
 ### Read-Only
 
-- `env` (List of String) Computed envbuilder configuration to be set for the container.
+- `env` (List of String, Sensitive) Computed envbuilder configuration to be set for the container. May contain secrets.
 - `exists` (Boolean) Whether the cached image was exists or not for the given config.
 - `id` (String) Cached image identifier. This will generally be the image's SHA256 digest.
 - `image` (String) Outputs the cached image repo@digest if it exists, and builder image otherwise.

examples/data-sources/envbuilder_cached_image/data-source.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
+}