test: add unit tests for attestation type processors (JUnit, Snyk, SonarQube, Jira)

[Copilot]

Four attestation processors (JunitAttestationProcessor, SnykAttestationProcessor, SonarAttestationProcessor, JiraAttestationProcessor) had no test coverage.

Tests added

Each test class is a pure unit test (no Spring context) directly instantiating the processor under test.

• JunitAttestationProcessorTest — passing XML, failures/errors > 0 → FAILED, malformed XML, empty document
• SnykAttestationProcessorTest — SARIF and Snyk JSON formats; 0 vulns → PASSED, >0 → FAILED, malformed JSON
• SonarAttestationProcessorTest — flat {"status":"OK/ERROR"} and nested {"projectStatus":{"status":...}}; PASSED string alias; malformed JSON
• JiraAttestationProcessorTest — valid/invalid [A-Z]+-\d+ key as plain text and within JSON issueRef; malformed JSON

All processors follow the same contract: parse input, set attestation.status, populate attestation.details, and fall through to FAILED with an "error" detail on any parse exception.

@Test
fun `malformed XML sets status FAILED with error details`() {
    val attestation = makeAttestation()
    processor.process("<<not valid xml!!>>".toByteArray(), attestation)

    assertEquals(AttestationStatus.FAILED, attestation.status)
    assertTrue(attestation.details!!.contains("error"))
}

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