Feat/add datasource to query machine types (#968)

* feat(iaas): add datasource to query machine types

Signed-off-by: Mauritz Uphoff <mauritz.uphoff@stackit.cloud>

* review

Signed-off-by: Mauritz Uphoff <mauritz.uphoff@stackit.cloud>

* review

Signed-off-by: Mauritz Uphoff <mauritz.uphoff@stackit.cloud>

---------

Signed-off-by: Mauritz Uphoff <mauritz.uphoff@stackit.cloud>

docs/data-sources/machine_type.md

@@ -0,0 +1,70 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "stackit_machine_type Data Source - stackit"
+subcategory: ""
+description: |-
+  Machine type data source.
+  ~> This datasource 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_machine_type (Data Source)
+
+Machine type data source.
+
+~> This datasource 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_machine_type" "two_vcpus_filter" {
+  project_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  filter     = "vcpus==2"
+}
+
+data "stackit_machine_type" "filter_sorted_ascending_false" {
+  project_id     = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  filter         = "vcpus >= 2 && ram >= 2048"
+  sort_ascending = false
+}
+
+data "stackit_machine_type" "intel_icelake_generic_filter" {
+  project_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  filter     = "extraSpecs.cpu==\"intel-icelake-generic\" && vcpus == 2"
+}
+
+# returns warning
+data "stackit_machine_type" "no_match" {
+  project_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+  filter     = "vcpus == 99"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `filter` (String) Expr-lang filter for filtering machine types.
+
+Examples:
+- vcpus == 2
+- ram >= 2048
+- extraSpecs.cpu == "intel-icelake-generic"
+- extraSpecs.cpu == "intel-icelake-generic" && vcpus == 2
+
+See https://expr-lang.org/docs/language-definition for syntax.
+- `project_id` (String) STACKIT Project ID.
+
+### Optional
+
+- `sort_ascending` (Boolean) Sort machine types by name ascending (`true`) or descending (`false`). Defaults to `false`
+
+### Read-Only
+
+- `description` (String) Machine type description.
+- `disk` (Number) Disk size in GB.
+- `extra_specs` (Map of String) Extra specs (e.g., CPU type, overcommit ratio).
+- `id` (String) Terraform's internal resource ID. It is structured as "`project_id`,`image_id`".
+- `name` (String) Name of the machine type (e.g. 's1.2').
+- `ram` (Number) RAM size in MB.
+- `vcpus` (Number) Number of vCPUs.