feat(api): add Intel DCAP API client module

Introduced a new `intel-dcap-api` crate for interacting with Intel's DCAP APIs.
- Implemented various API client functionalities for SGX/TDX attestation services.
- Added support for registration, certification, enclave identity, and FMSPC retrieval.

Signed-off-by: Harald Hoyer <harald@matterlabs.dev>

crates/intel-dcap-api/examples/example.rs

@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (c) 2025 Matter Labs
+
+use intel_dcap_api::{
+    ApiClient, ApiVersion, CaType, CrlEncoding, EnclaveIdentityResponse, IntelApiError,
+    PckCrlResponse, PlatformFilter, TcbInfoResponse,
+};
+
+#[tokio::main]
+async fn main() -> Result<(), IntelApiError> {
+    for api_version in [ApiVersion::V3, ApiVersion::V4] {
+        println!("Using API version: {}", api_version);
+
+        let client = ApiClient::new_with_version(api_version)?;
+
+        // Example: Get SGX TCB Info
+        let fmspc_example = "00606A000000"; // Example FMSPC from docs
+        match client.get_sgx_tcb_info(fmspc_example, None, None).await {
+            Ok(TcbInfoResponse {
+                tcb_info_json,
+                issuer_chain,
+            }) => println!(
+                "SGX TCB Info for {}:\n{}\nIssuer Chain: {}",
+                fmspc_example, tcb_info_json, issuer_chain
+            ),
+            Err(e) => eprintln!("Error getting SGX TCB info: {}", e),
+        }
+
+        // Example: Get FMSPCs
+        match client.get_fmspcs(Some(PlatformFilter::E3)).await {
+            // Filter for E3 platform type [cite: 230]
+            Ok(fmspc_list) => println!("\nE3 FMSPCs:\n{}", fmspc_list),
+            Err(e) => eprintln!("Error getting FMSPCs: {}", e),
+        }
+
+        // Example: Get SGX QE Identity
+        match client.get_sgx_qe_identity(None, None).await {
+            Ok(EnclaveIdentityResponse {
+                enclave_identity_json,
+                issuer_chain,
+            }) => {
+                println!(
+                    "\nSGX QE Identity:\n{}\nIssuer Chain: {}",
+                    enclave_identity_json, issuer_chain
+                )
+            }
+            Err(e) => eprintln!("Error getting SGX QE Identity: {}", e),
+        }
+
+        // Example: Get PCK CRL (Platform CA, PEM encoding)
+        match client
+            .get_pck_crl(CaType::Platform, Some(CrlEncoding::Pem))
+            .await
+        {
+            // [cite: 118, 119]
+            Ok(PckCrlResponse {
+                crl_data,
+                issuer_chain,
+            }) => {
+                // Attempt to decode PEM for display, otherwise show byte count
+                match String::from_utf8(crl_data.clone()) {
+                    Ok(pem_string) => println!(
+                        "\nPlatform PCK CRL (PEM):\n{}\nIssuer Chain: {}",
+                        pem_string, issuer_chain
+                    ),
+                    Err(_) => println!(
+                        "\nPlatform PCK CRL ({} bytes, likely DER):\nIssuer Chain: {}",
+                        crl_data.len(),
+                        issuer_chain
+                    ),
+                }
+            }
+            Err(e) => eprintln!("Error getting PCK CRL: {}", e),
+        }
+    }
+
+    Ok(())
+}