FINERACT-1152: Loan Rescheduling End Date Validation Fix

[DeathGun44]

Description

Resolves FINERACT-1152.

The core issue here was that you couldn't extend a loan's tenure (extraTerms) and change its EMI at the same time because the validation threw an error if the new endDate didn't already exist in the schedule.

What I changed:

1. Relaxed End Date Validation: Tweaked LoanRescheduleRequestDataValidatorImpl so that if extraTerms > 0, we allow the endDate to fall on a future, projected installment date.
2. Blanket EMI Variations: The old logic tried to map new EMIs to specific existing installments using a loop. I rewrote LoanRescheduleRequestWritePlatformServiceImpl to use a blanket term variation instead (isSpecificToInstallment=false). Now, the schedule generator will naturally apply the new EMI across all future installments, including the newly requested ones.
3. Fineract-Client & Tests: To properly test this, I realized the Swagger API docs were missing the emi and endDate fields for rescheduling requests. I added them in, regenerated the fineract-client SDK, and then wrote a modern integration test (testCreateLoanRescheduleChangeEMIWithExtraTerms) bypassing the legacy RestAssured models to prove the fix works perfectly!

Checklist

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• Add required Swagger annotation and update API documentation
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