enable declaring custom topics for ffi interface publish and ff publish api create

[ka1ii]

Proposed changes

allow clients to declare custom topics for ffi interface publish and ff publish api create

Fixes #1725

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Types of changes

• [ x] Bug fix
• [ x] New feature added
• [ x] Documentation Update

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• I have read the contributing guidelines.
• [x ] I have performed a self-review of my own code or work.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generates no new warnings.
• [ x] I have added tests that prove my fix is effective or that my feature works.
• [ x] My changes have sufficient code coverage (unit, integration, e2e tests).

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