feat: add tenant id header to next invocation request

Author: Ramisa Alam

include/aws/lambda-runtime/runtime.h

@@ -61,6 +61,11 @@ struct invocation_request {
      */
     std::chrono::time_point<std::chrono::system_clock> deadline;
 
+    /**
+    * Tenant ID of the current invocation.
+     */
+    std::string tenant_id;
+
     /**
      * The number of milliseconds left before lambda terminates the current execution.
      */

src/runtime.cpp

@@ -41,6 +41,7 @@ static constexpr auto CLIENT_CONTEXT_HEADER = "lambda-runtime-client-context";
 static constexpr auto COGNITO_IDENTITY_HEADER = "lambda-runtime-cognito-identity";
 static constexpr auto DEADLINE_MS_HEADER = "lambda-runtime-deadline-ms";
 static constexpr auto FUNCTION_ARN_HEADER = "lambda-runtime-invoked-function-arn";
+static constexpr auto TENANT_ID_HEADER = "lambda-runtime-aws-tenant-id";
 
 enum Endpoints {
     INIT,
@@ -315,6 +316,12 @@ runtime::next_outcome runtime::get_next()
             req.payload.c_str(),
             static_cast<int64_t>(req.get_time_remaining().count()));
     }
+
+    out = resp.get_header(TENANT_ID_HEADER);
+    if (out.is_success()) {
+        req.tenant_id = std::move(out).get_result();
+    }
+
     return {req};
 }