🛡️ Sentinel: Enhance input validation and error sanitization

[google-labs-jules]

🛡️ Sentinel: Security Enhancement

🚨 Severity: MEDIUM

💡 Vulnerability:

1. Weak input validation on entity identifiers (IDs) could allow malformed input or potential injection-style attacks.
2. Verbose error messages in some handlers could leak internal validation details (like Pydantic error types).

🎯 Impact:

1. Maliciously crafted IDs might cause unexpected behavior in downstream services or database queries.
2. Information leakage via error messages aids attackers in reconnaissance.

🔧 Fix:

1. Enforced a strict alphanumeric/hyphen/underscore pattern on the base Entity.id model.
2. Added proactive validation at the entry point of Bedrock Agent and GraphQL handlers.
3. Standardized error responses to return a generic "Invalid item ID" while logging specific validation errors as warnings.
4. Ensured consistent serialization by using .dump() in the SQS handler.

✅ Verification:

1. Ran uv run pytest - all 71 tests passed (including 3 new test cases).
2. Ran uv run ruff check . and uv run ruff format . - code follows standards.
3. Manually verified that providing an ID like abc! now correctly triggers a 400/error response with a sanitized message.

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PR created automatically by Jules for task 5062270033042870225 started by @amrabed

[google-labs-jules]

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