fix: add null validation for telemetry parameter

Add null checks for the telemetry parameter in the new
ApiExecutor and HttpRequestAttempt constructors, consistent
with existing validation of other parameters.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jimmyjames

src/main/java/dev/openfga/sdk/api/client/ApiExecutor.java

@@ -56,6 +56,9 @@ public ApiExecutor(ApiClient apiClient, Configuration configuration, Telemetry t
         if (configuration == null) {
             throw new IllegalArgumentException("Configuration cannot be null");
         }
+        if (telemetry == null) {
+            throw new IllegalArgumentException("Telemetry cannot be null");
+        }
         this.apiClient = apiClient;
         this.configuration = configuration;
         this.telemetry = telemetry;

src/main/java/dev/openfga/sdk/api/client/HttpRequestAttempt.java

@@ -49,6 +49,9 @@ public HttpRequestAttempt(
             Telemetry telemetry)
             throws FgaInvalidParameterException {
         assertParamExists(configuration.getMaxRetries(), "maxRetries", "Configuration");
+        if (telemetry == null) {
+            throw new IllegalArgumentException("Telemetry cannot be null");
+        }
         this.apiClient = apiClient;
         this.configuration = configuration;
         this.name = name;