Add Convert and downstream test

What does this MR do?

• Add unit tests for Convert function
• Adds tests/java-android as downstream test project (see companion MR gitlab-org/security-products/tests/java-android!8 (merged))

What are the relevant issue numbers?

• Issue: gitlab-org/gitlab#259833 (closed)
• Issue: gitlab-org/gitlab#268395 (closed)

Does this MR meet the acceptance criteria?

• [-] Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
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• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer