Add OPENAI_API_KEY properties

Author: danieloh30

scaffolder-templates/agentic-ai-template/skeleton/src/main/resources/application.properties

@@ -36,6 +36,7 @@ quarkus.langchain4j.mcp.time.command=uvx,mcp-server-time
 quarkus.langchain4j.chat-model.provider=openai
 quarkus.langchain4j.openai.chat-model.temperature=0.8
 quarkus.langchain4j.openai.chat-model.model-name=gpt-4o-mini
+quarkus.langchain4j.openai.api-key=${OPENAI_API_KEY}
 quarkus.langchain4j.openai.log-requests=true
 quarkus.langchain4j.openai.log-responses=true
 quarkus.log.category.\"dev.langchain4j\".level=DEBUG