Amazon Bedrock AgentCore Samples - Amazon ECS with AgentCore Identity and 3LO

**Describe the tutorial request**
This sample demonstrates how to build an AI agent on Amazon ECS that uses **[Amazon Bedrock AgentCore Identity](https://docs.aws.amazon.com/bedrock-agentcore/latest/devguide/identity-getting-started.html)** for **3-Legged OAuth (3LO)** authorization. The agent can securely access external services (like GitHub) on behalf of authenticated users. IaC provided via CDK.

in collaboration with @satveerkhurpa

**Is this feature already supported by the AgentCore service?**
- [x] Yes
- [ ] No

If `yes`, please provide any appropriate documentation link.