Add Beta annotation to new public API

Author: a-d

core/src/main/java/com/sap/ai/sdk/core/commons/ClientError.java

@@ -1,12 +1,15 @@
 package com.sap.ai.sdk.core.commons;
 
+import com.google.common.annotations.Beta;
 import javax.annotation.Nonnull;
 
 /**
  * Generic class that contains a JSON error response.
  *
  * @since 1.1.0
  */
+@Beta
+@FunctionalInterface
 public interface ClientError {
   /**
    * Get the error message.

core/src/main/java/com/sap/ai/sdk/core/commons/ClientException.java

@@ -1,11 +1,13 @@
 package com.sap.ai.sdk.core.commons;
 
+import com.google.common.annotations.Beta;
 import lombok.experimental.StandardException;
 
 /**
  * Generic exception for errors occurring when using AI SDK clients.
  *
  * @since 1.1.0
  */
+@Beta
 @StandardException
 public class ClientException extends RuntimeException {}

core/src/main/java/com/sap/ai/sdk/core/commons/ClientResponseHandler.java

@@ -4,6 +4,7 @@
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.annotations.Beta;
 import io.vavr.control.Try;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
@@ -26,6 +27,7 @@
  * @param <E> The type of the exception to throw
  * @since 1.1.0
  */
+@Beta
 @Slf4j
 @RequiredArgsConstructor
 public class ClientResponseHandler<T, E extends ClientException>