terraform-provider: add attestation data source (#2640)

Signed-off-by: Daniel Weiße <dw@edgeless.systems>
Co-authored-by: Daniel Weiße <dw@edgeless.systems>

terraform-provider-constellation/docs/data-sources/attestation.md

@@ -0,0 +1,76 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "constellation_attestation Data Source - constellation"
+subcategory: ""
+description: |-
+  The data source to fetch measurements from a configured cloud provider and image.
+---
+
+# constellation_attestation (Data Source)
+
+The data source to fetch measurements from a configured cloud provider and image.
+
+## Example Usage
+
+```terraform
+data "constellation_attestation" "test" {
+  csp                 = "aws"
+  attestation_variant = "aws-sev-snp"
+  image_version       = "v2.13.0"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `attestation_variant` (String) Attestation variant the image should work with. Can be one of:
+  * `aws-sev-snp`
+  * `aws-nitro-tpm`
+  * `azure-sev-snp`
+  * `gcp-sev-es`
+- `csp` (String) CSP (Cloud Service Provider) to use. (e.g. `azure`)
+See the [full list of CSPs](https://docs.edgeless.systems/constellation/overview/clouds) that Constellation supports.
+- `image_version` (String) The image version to use
+
+### Optional
+
+- `maa_url` (String) For Azure only, the URL of the Microsoft Azure Attestation service
+
+### Read-Only
+
+- `attestation` (Attributes) Only relevant for SEV-SNP. (see [below for nested schema](#nestedatt--attestation))
+- `id` (String) The ID of the data source
+- `measurements` (Attributes Map) (see [below for nested schema](#nestedatt--measurements))
+
+<a id="nestedatt--attestation"></a>
+### Nested Schema for `attestation`
+
+Read-Only:
+
+- `amd_root_key` (String)
+- `azure_firmware_signer_config` (Attributes) (see [below for nested schema](#nestedatt--attestation--azure_firmware_signer_config))
+- `bootloader_version` (Number)
+- `microcode_version` (Number)
+- `snp_version` (Number)
+- `tee_version` (Number)
+
+<a id="nestedatt--attestation--azure_firmware_signer_config"></a>
+### Nested Schema for `attestation.azure_firmware_signer_config`
+
+Read-Only:
+
+- `accepted_key_digests` (List of String)
+- `enforcement_policy` (String)
+- `maa_url` (String)
+
+
+
+<a id="nestedatt--measurements"></a>
+### Nested Schema for `measurements`
+
+Read-Only:
+
+- `expected` (String)
+- `warn_only` (Boolean)