Add oracle price deviation monitoring and circuit breaker

[Smartdevs17]

Description

Oracle price manipulation or failure can cause incorrect liquidations. Implement monitoring with automatic circuit breaker on price anomalies.

Acceptance Criteria

• Price deviation between sources >2% triggers alert
• Price deviation >10% triggers automatic pause
• Staleness detection (no update for >1 hour)
• Price volatility circuit breaker (>20% change in 10min)
• Gradual unpause after price stabilization
• Oracle incident report generation

Technical Scope

• oracle/src/security/
• stellar-lend/contracts/hello-world/src/oracle.rs
• Edge: legitimate volatility (Flash Crash), multiple oracle simultaneous failure

[TUPM96]

Opened PR #400 for this: #400

Implemented source deviation alerts/pauses, volatility circuit breaker, stale-feed incident reports, gradual stabilization-based unpause, and queryable oracle incident reports.

[Smartdevs17]

Kingly wait till you're assigned before creating a pr.

[Josetic224]

@Josetic224 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi Smartdevs17,

I would love to take on this issue. Implementing robust oracle guardrails is critical for preventing erroneous liquidations and protecting protocol solvency. I have experience writing secure Soroban smart contracts and handling oracle data feeds.

Here is how I plan to approach the implementation within oracle/src/security/ and stellar-lend/contracts/hello-world/src/oracle.rs:

🛠️ Proposed Implementation Plan
Multi-Source Deviation Engine: Implement a comparison mechanism between the primary oracle and secondary/fallback sources.

2% Deviation: Emit a Soroban event to trigger off-chain alerting systems.

10% Deviation: Automatically flip a state variable to Paused, freezing liquidation and borrowing functions.

Staleness & Volatility Circuit Breakers: * Track the last_updated_timestamp to enforce a 1-hour strict staleness check.

Maintain a rolling window or historical price checkpoints within contract storage to detect >20% price movements within a 10-minute window.

Gradual Recovery & Reporting:

Implement a cooled-down, phased unpausing mechanism requiring price stabilization for a set period (or a multi-sig override if necessary).

Create a structured IncidentReport event containing the failed price, timestamps, and source deviations for off-chain logging.

⚡ Handling Edge Cases
Legitimate Volatility vs. Manipulation: During a flash crash, if multiple independent sources agree on the >20% drop, the circuit breaker should still pause to allow the protocol to breathe, but the recovery mechanism will recognize the consensus once stabilized.

Simultaneous Failures: If multiple oracles fail or become stale simultaneously, the contract will default to a safe, fully paused state rather than relying on a single unverified "surviving" feed.

I am ready to start on this immediately and will ensure comprehensive test coverage for all deviation thresholds and edge cases. Could you please assign this issue to me?

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Josetic224 to this issue.