fix Params lint error

[Mshehu5]

This PR Closes #1162

Problem

The function identify_receiver_outputs was modifying a local copy of params but never using the modified version, causing a linter error. The issue was that the function signature only returned Vec<usize> (the owned_vouts), so the modified params were lost.

This also stops the lint and lint ffi test workflow to fail

Looking at the logic, it looks like the intention was to modify the params to remove the additional_fee_contribution if it points to a receiver output. However, since the function couldn't return the modified params, the modification was useless.

Solution

• Changed the return type of identify_receiver_outputs from Result<Vec<usize>, Error> to Result<(Vec<usize>, Self), Error> to return both the owned vouts and the filtered payload.

• Created variable original_payload by constructing a new Self instance with the modified params

• Updated the return statement** to return both values

• Updated all callers in the codebase to handle the new return type In v1/mod.rs,In v2/mod.rs

the lint test also passes in my branch test workflow : https://github.com/Mshehu5/rust-payjoin/actions/runs/18546726647

Please confirm the following before requesting review:

• I have disclosed my use of AI in the body of this PR.
• I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

[coveralls]

Pull Request Test Coverage Report for Build 18551723885

Details

• 12 of 19 (63.16%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 83.742%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
payjoin/src/core/receive/v2/mod.rs	6	13	46.15%

Totals
Change from base Build 18413003453:	0.005%
Covered Lines:	8957
Relevant Lines:	10696

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💛 - Coveralls

[benalleng]

Have we considered not just allowing mut self in the function definitions?

[Mshehu5]

Have we considered not just allowing mut self in the function definitions?

Thank you for the insight !
yeah seems that's a simpler way to solve it
but will this have any effect on the state machine by making mut self in the function mutable ?

[benalleng]

Yeah, this obviously is something to consider as this is a pub fn, perhaps others have some stronger opinions if this is a no go.