Add invoice automated market maker

[Kingsman-99]

Label: complexity: high
Points: 200

Description

Released invoice proceeds sit idle until recipients manually move them. This issue adds amm_on_release: bool — when set, _release() deposits each recipient's share into an AMM liquidity pool contract, providing instant liquidity and yield on released funds.

Technical Context

Involves lib.rs _release(). Store amm_contract: Option<Address> in persistent storage. When invoice.amm_on_release is true and amm_contract is set, for each recipient call amm_contract.add_liquidity(recipient, amount) instead of direct transfer. Use mock AMM contract in tests.

Acceptance Criteria

• create_invoice() accepts amm_on_release: bool
• _release() calls AMM contract for each recipient when flag set
• Direct transfer used when amm_on_release = false
• AMM contract failure reverts the release
• Test mocks AMM contract and verifies it is called with correct recipient and amount
• All existing cargo tests pass
• cargo clippy passes with zero warnings

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[Dydex]

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

Hi Maintainer, Pls I can work on this issue

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[Blaqkenny]

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

Hello Maintainer, please can I work on this issue and give you a better result

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[Cjay-Cyber-2]

@Cjay-Cyber-2 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

hey i would love to work on this issue

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[Sendi0011]

@Sendi0011 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Gm team, i will like to work on this, i am a frontend/smartcontract developer with experience skill solving issues like this. i am also an active Open source contributor.
ETA: 4 hours

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Sendi0011 to this issue.