Feature: CDN distribution resource and data source (#786)

* add datasource

* finish data source

* implement resource

* add unit tests

* add examples

* acceptance test

* review comments

* review comments 2

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Co-authored-by: Malte Ehrlen <malte.ehrlen@freiheit.com>

docs/data-sources/cdn_distribution.md

@@ -0,0 +1,70 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "stackit_cdn_distribution Data Source - stackit"
+subcategory: ""
+description: |-
+  CDN distribution data source schema.
+  ~> This resource is in beta and may be subject to breaking changes in the future. Use with caution. See our guide https://registry.terraform.io/providers/stackitcloud/stackit/latest/docs/guides/opting_into_beta_resources for how to opt-in to use beta resources.
+---
+
+# stackit_cdn_distribution (Data Source)
+
+CDN distribution data source schema.
+
+~> This resource is in beta and may be subject to breaking changes in the future. Use with caution. See our [guide](https://registry.terraform.io/providers/stackitcloud/stackit/latest/docs/guides/opting_into_beta_resources) for how to opt-in to use beta resources.
+
+## Example Usage
+
+```terraform
+data "stackit_cdn_distribution" "example" {
+  project_id      = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  distribution_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `distribution_id` (String) STACKIT project ID associated with the distribution
+- `project_id` (String) STACKIT project ID associated with the distribution
+
+### Read-Only
+
+- `config` (Attributes) The distribution configuration (see [below for nested schema](#nestedatt--config))
+- `created_at` (String) Time when the distribution was created
+- `domains` (Attributes List) List of configured domains for the distribution (see [below for nested schema](#nestedatt--domains))
+- `errors` (List of String) List of distribution errors
+- `id` (String) Terraform's internal resource identifier. It is structured as "`project_id`,`distribution_id`".
+- `status` (String) Status of the distribution
+- `updated_at` (String) Time when the distribution was last updated
+
+<a id="nestedatt--config"></a>
+### Nested Schema for `config`
+
+Read-Only:
+
+- `backend` (Attributes) The configured backend for the distribution (see [below for nested schema](#nestedatt--config--backend))
+- `regions` (List of String) The configured regions where content will be hosted
+
+<a id="nestedatt--config--backend"></a>
+### Nested Schema for `config.backend`
+
+Read-Only:
+
+- `origin_request_headers` (Map of String) The configured origin request headers for the backend
+- `origin_url` (String) The configured backend type for the distribution
+- `type` (String) The configured backend type
+
+
+
+<a id="nestedatt--domains"></a>
+### Nested Schema for `domains`
+
+Read-Only:
+
+- `errors` (List of String) List of domain errors
+- `name` (String) The name of the domain
+- `status` (String) The status of the domain
+- `type` (String) The type of the domain. Each distribution has one domain of type "managed", and domains of type "custom" may be additionally created by the user