Adds OllamaStream handling

src/main/java/io/github/amithkoujalgi/ollama4j/core/OllamaStreamHandler.java

@@ -0,0 +1,7 @@
+package io.github.amithkoujalgi.ollama4j.core;
+
+import java.util.function.Consumer;
+
+public interface OllamaStreamHandler extends Consumer<String>{
+    void accept(String message);
+}

src/main/java/io/github/amithkoujalgi/ollama4j/core/models/chat/OllamaChatStreamObserver.java

@@ -0,0 +1,34 @@
+package io.github.amithkoujalgi.ollama4j.core.models.chat;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import io.github.amithkoujalgi.ollama4j.core.OllamaStreamHandler;
+import lombok.NonNull;
+
+public class OllamaChatStreamObserver {
+
+    private OllamaStreamHandler streamHandler;
+
+    private List<OllamaChatResponseModel> responseParts = new ArrayList<>();
+
+    private String message;
+
+    public OllamaChatStreamObserver(OllamaStreamHandler streamHandler) {
+        this.streamHandler = streamHandler;
+    }
+
+    public void notify(OllamaChatResponseModel currentResponsePart){
+        responseParts.add(currentResponsePart);
+        handleCurrentResponsePart(currentResponsePart);
+    }
+    
+    protected void handleCurrentResponsePart(OllamaChatResponseModel currentResponsePart){
+        List<@NonNull String> allResponsePartsByNow = responseParts.stream().map(r -> r.getMessage().getContent()).collect(Collectors.toList());
+        message = String.join("", allResponsePartsByNow);
+        streamHandler.accept(message);
+    }
+
+
+}