Onboard MongoDB Flex user (#88)

* Onboard user

* Add examples and generate docs

* Adjustments after review

docs/data-sources/mongodbflex_instance.md

@@ -0,0 +1,68 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "stackit_mongodbflex_instance Data Source - stackit"
+subcategory: ""
+description: |-
+  MongoDB Flex instance data source schema.
+---
+
+# stackit_mongodbflex_instance (Data Source)
+
+MongoDB Flex instance data source schema.
+
+## Example Usage
+
+```terraform
+data "stackit_mongodbflex_instance" "example" {
+  project_id  = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  instance_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  user_id     = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `instance_id` (String) ID of the MongoDB Flex instance.
+- `project_id` (String) STACKIT project ID to which the instance is associated.
+
+### Read-Only
+
+- `acl` (List of String) The Access Control List (ACL) for the MongoDB Flex instance.
+- `backup_schedule` (String)
+- `flavor` (Attributes) (see [below for nested schema](#nestedatt--flavor))
+- `id` (String) Terraform's internal data source. ID. It is structured as "`project_id`,`instance_id`".
+- `name` (String) Instance name.
+- `options` (Attributes) (see [below for nested schema](#nestedatt--options))
+- `replicas` (Number)
+- `storage` (Attributes) (see [below for nested schema](#nestedatt--storage))
+- `version` (String)
+
+<a id="nestedatt--flavor"></a>
+### Nested Schema for `flavor`
+
+Read-Only:
+
+- `cpu` (Number)
+- `description` (String)
+- `id` (String)
+- `ram` (Number)
+
+
+<a id="nestedatt--options"></a>
+### Nested Schema for `options`
+
+Read-Only:
+
+- `type` (String)
+
+
+<a id="nestedatt--storage"></a>
+### Nested Schema for `storage`
+
+Read-Only:
+
+- `class` (String)
+- `size` (Number)

docs/data-sources/mongodbflex_user.md

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+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "stackit_mongodbflex_user Data Source - stackit"
+subcategory: ""
+description: |-
+  PostgresFlex user data source schema.
+---
+
+# stackit_mongodbflex_user (Data Source)
+
+PostgresFlex user data source schema.
+
+## Example Usage
+
+```terraform
+data "stackit_mongodbflex_instance" "example" {
+  project_id  = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  instance_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `instance_id` (String) ID of the PostgresFlex instance.
+- `project_id` (String) STACKIT project ID to which the instance is associated.
+- `user_id` (String) User ID.
+
+### Read-Only
+
+- `database` (String)
+- `host` (String)
+- `id` (String) Terraform's internal data source. ID. It is structured as "`project_id`,`instance_id`,`user_id`".
+- `port` (Number)
+- `roles` (Set of String)
+- `username` (String)