Anthropic allows multiple system messages, simplify

integrations/anthropic/src/haystack_integrations/components/generators/anthropic/chat/chat_generator.py

@@ -179,20 +179,20 @@ def run(self, messages: List[ChatMessage], generation_kwargs: Optional[Dict[str,
                 f"Model parameters {disallowed_params} are not allowed and will be ignored. "
                 f"Allowed parameters are {self.ALLOWED_PARAMS}."
             )
-
-        # adapt ChatMessage(s) to the format expected by the Anthropic API
-        anthropic_formatted_messages = self._convert_to_anthropic_format(messages)
-
-        # system message provided by the user overrides the system message from the self.generation_kwargs
-        system = [anthropic_formatted_messages[0]] if messages and messages[0].is_from(ChatRole.SYSTEM) else None
-        if system:
-            anthropic_formatted_messages = anthropic_formatted_messages[1:]
+        system_messages: List[ChatMessage] = [msg for msg in messages if msg.is_from(ChatRole.SYSTEM)]
+        non_system_messages: List[ChatMessage] = [msg for msg in messages if not msg.is_from(ChatRole.SYSTEM)]
+        system_messages_formatted: List[Dict[str, Any]] = (
+            self._convert_to_anthropic_format(system_messages) if system_messages else []
+        )
+        messages_formatted: List[Dict[str, Any]] = (
+            self._convert_to_anthropic_format(non_system_messages) if non_system_messages else []
+        )
 
         response: Union[Message, Stream[MessageStreamEvent]] = self.client.messages.create(
             max_tokens=filtered_generation_kwargs.pop("max_tokens", 512),
-            system=system if system else filtered_generation_kwargs.pop("system", ""),
+            system=system_messages_formatted or filtered_generation_kwargs.pop("system", ""),
             model=self.model,
-            messages=anthropic_formatted_messages,
+            messages=messages_formatted,
             stream=self.streaming_callback is not None,
             **filtered_generation_kwargs,
         )
@@ -261,14 +261,15 @@ def _convert_to_anthropic_format(self, messages: List[ChatMessage]) -> List[Dict
         anthropic_formatted_messages = []
         for m in messages:
             message_dict = dataclasses.asdict(m)
-            filtered_message = {k: v for k, v in message_dict.items() if k in {"role", "content"} and v}
+            formatted_message = {k: v for k, v in message_dict.items() if k in {"role", "content"} and v}
             if m.is_from(ChatRole.SYSTEM):
                 # system messages need to be in the format expected by the Anthropic API
-                filtered_message.pop("role")
-                filtered_message["type"] = "text"
-                filtered_message["text"] = filtered_message.pop("content")
-            filtered_message.update(m.meta or {})
-            anthropic_formatted_messages.append(filtered_message)
+                # remove role and content from the message dict, add type and text
+                formatted_message.pop("role")
+                formatted_message["type"] = "text"
+                formatted_message["text"] = formatted_message.pop("content")
+            formatted_message.update(m.meta or {})
+            anthropic_formatted_messages.append(formatted_message)
         return anthropic_formatted_messages
 
     def _connect_chunks(