fix: correct bank entry calculation with deductions and prevent multiple loan repayment deductions

[Nihantra-Patel]

Introduced via #2283 & #2324 and loan flow.

Issue:

• When deductions were present, the bank entry calculation did not work as expected.
• total_loan_repayment was being subtracted multiple times for each salary detail, leading to an incorrect salary_slip_total in the bank entry.

Resolution:

• Adjusted the get_salary_slip_details function to ensure total_loan_repayment is fetched only once per unique salary slip.
• In the make_bank_entry function, we separated the total_loan_repayment deduction from the main loop, ensuring it’s only subtracted once per salary slip, after calculating the total of earnings and deductions.

[ruchamahabal]

Can you add a test to ensure this doesn't break?

[Nihantra-Patel]

Can you add a test to ensure this doesn't break?

added in previous PR: https://github.com/frappe/hrms/pull/2283/files#diff-cf6a883b62bb2053bba145dc2c7501552ea94f0b170188dd3a8d8ce1771028c1

[ruchamahabal]

added in previous PR: #2283 (files)

The test is mostly of no use since it doesn't assert the loan amount deduction from salary slip total. Else, the above error could have been caught with the test

[ruchamahabal]

Thanks for being patient with the review 🙈 :D

[ruchamahabal]

@Mergifyio backport version-15

[mergify]

backport version-15

✅ Backports have been created

• #2356 fix: correct bank entry calculation with deductions and prevent multiple loan repayment deductions (backport #2347) has been created for branch version-15 but encountered conflicts