Feature: CDN custom domain resource and data source (#801)

* Feature: CDN custom domain resource and data source

* stabilize acceptance tests

* add guide

* review changes

---------

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

docs/data-sources/cdn_custom_domain.md

@@ -0,0 +1,39 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "stackit_cdn_custom_domain 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_custom_domain (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_custom_domain" "example" {
+  project_id      = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  distribution_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  name            = "https://xxx.xxx"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `distribution_id` (String) CDN distribution ID
+- `name` (String)
+- `project_id` (String) STACKIT project ID associated with the distribution
+
+### Read-Only
+
+- `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

docs/guides/stackit_cdn_with_custom_domain.md

@@ -0,0 +1,60 @@
+---
+page_title: "Using STACKIT CDN with your own domain"
+---
+# Using STACKIT CDN with your own domain
+
+## Overview
+
+This guide outlines the process of creating a STACKIT CDN distribution and configuring it to make use of an existing domain using STACKIT DNS.
+
+## Steps
+
+1. **Create a STACKIT CDN and DNS Zone**
+    
+    Create the CDN distribution and the DNS zone.
+    
+    ```terraform
+    resource "stackit_cdn_distribution" "example_distribution" {
+      project_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+      config = {
+        backend = {
+          type       = "http"
+          origin_url = "mybackend.onstackit.cloud"
+        }
+        regions = ["EU", "US", "ASIA", "AF", "SA"]
+      }
+    }
+    
+    resource "stackit_dns_zone" "example_zone" {
+      project_id    = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+      name          = "My DNS zone"
+      dns_name      = "myapp.runs.onstackit.cloud"
+      contact_email = "aa@bb.ccc"
+      type          = "primary"
+    }
+    ```
+    
+2. **Add CNAME record to your DNS zone**
+
+    If you want to redirect your entire domain to the CDN, you can instead use an A record.
+    ```terraform
+    resource "stackit_dns_record_set" "example" {
+      project_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+      zone_id    = stackit_dns_zone.example_zone.zone_id
+      name       = "cdn"
+      type       = "CNAME"
+      records    = ["${stackit_cdn_distribution.domains[0].name}."]
+    }
+    ```
+    
+3. **Create a STACKIT CDN Custom Domain**
+    ```terraform
+    # Create a CDN custom domain
+    resource "stackit_cdn_custom_domain" "example" {
+      project_id      = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+      distribution_id = stackit_cdn_distribution.example_distribution.distribution_id
+      name            = "${stackit_dns_record_set.example.name}.${stackit_dns_zone.dns_name}"
+    }
+    ```
+    
+    Now, you can access your content on the url `cdn.myapp.runs.onstackit.cloud`.

docs/resources/cdn_custom_domain.md

@@ -0,0 +1,40 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "stackit_cdn_custom_domain Resource - 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_custom_domain (Resource)
+
+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
+# Create a CDN custom domain
+resource "stackit_cdn_custom_domain" "example" {
+  project_id      = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  distribution_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  name            = "https://xxx.xxx"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `distribution_id` (String) CDN distribution ID
+- `name` (String)
+- `project_id` (String) STACKIT project ID associated with the distribution
+
+### Read-Only
+
+- `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

docs/resources/cdn_distribution.md

@@ -40,7 +40,7 @@ resource "stackit_cdn_distribution" "example_distribution" {
 ### Read-Only
 
 - `created_at` (String) Time when the distribution was created
-- `distribution_id` (String) STACKIT project ID associated with the distribution
+- `distribution_id` (String) CDN distribution ID
 - `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`".