Add harness sample: JWT inbound auth + OAuth-protected gateway

[dhegde-aws]

Summary

Add a sample notebook demonstrating AgentCore harness with end-to-end OAuth integration:

• Inbound auth: CUSTOM_JWT authorizer on the harness (Cognito user pool, USER_PASSWORD_AUTH)
• Outbound auth: OAuth client credentials grant to authenticate to an AgentCore Gateway via a credential provider in AgentCore Identity

What the sample covers

• Configuring authorizerConfiguration.customJWTAuthorizer on a harness
• Configuring outboundAuth.oauth on a gateway tool with CLIENT_CREDENTIALS grant
• Registering an OAuth2 credential provider in AgentCore Identity
• Creating a Gateway with CUSTOM_JWT inbound auth and a Lambda target
• Invoking the harness with a bearer token via the HTTPS endpoint
• Full cleanup (discover-by-name, idempotent)

Files

• harness_oauth_gateway.ipynb — main notebook (focused on harness auth)
• utils/setup_helpers.py — idempotent infra setup functions (Cognito, Lambda, Gateway, IAM)
• utils/lambda_function_code.py — order management Lambda handler
• images/architecture.jpg — architecture diagram

Proposed location

[agentcore-samples] - [01-tutorials] - [11-AgentCore-harness] - [01-advanced-examples] - [07-oauth]