fix: add missing docs

docs/data-sources/postgresflexalpha_database.md

@@ -0,0 +1,40 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "stackitprivatepreview_postgresflexalpha_database Data Source - stackitprivatepreview"
+subcategory: ""
+description: |-
+  Postgres Flex database resource schema. Must have a region specified in the provider configuration.
+---
+
+# stackitprivatepreview_postgresflexalpha_database (Data Source)
+
+Postgres Flex database resource schema. Must have a `region` specified in the provider configuration.
+
+## Example Usage
+
+```terraform
+data "stackitprivatepreview_postgresflexalpha_database" "example" {
+  project_id  = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  instance_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  database_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `database_id` (String) Database ID.
+- `instance_id` (String) ID of the Postgres Flex instance.
+- `project_id` (String) STACKIT project ID to which the instance is associated.
+
+### Optional
+
+- `region` (String) The resource region. If not defined, the provider region is used.
+
+### Read-Only
+
+- `id` (String) Terraform's internal resource ID. It is structured as "`project_id`,`region`,`instance_id`,`database_id`".
+- `name` (String) Database name.
+- `owner` (String) Username of the database owner.