[contract] Add 3 Tests to oracle_tests.rs

[Olowodarey]

📋 Overview

Expand test coverage for the oracle module by adding 3 new tests.

✅ Tasks

• Add 3 new test functions to contract/tests/oracle_tests.rs
• Follow existing test patterns and helper functions
• Verify all tests pass

🧪 New Tests (3 total)

Test 1: Resolve Market With Invalid Outcome

#[test]
fn test_resolve_market_invalid_outcome() {
    // Create market with outcomes ["yes", "no"]
    // Try to resolve with outcome "maybe"
    // Should fail with invalid outcome error
}

Test 2: Resolve Already Resolved Market

#[test]
fn test_resolve_already_resolved_market() {
    // Create and resolve market
    // Try to resolve again
    // Should fail with already resolved error
}

Test 3: Resolve Market Before Resolution Time

#[test]
fn test_resolve_market_too_early() {
    // Create market with resolution_time in future
    // Try to resolve before resolution_time
    // Should fail with too early error
}

🔍 Verification

• All 3 tests written
• All tests pass
• Tests follow existing patterns
• No clippy warnings

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