FINERACT-2455: Working Capital loan discount field enhancement

[alberto-art3ch]

Description

The discount field is a single field introduced for Working Capital loans, which the user can enter/modify at the create/approve/disburse loan account steps. During modification, the original proposed amount was edited, and the history of the proposed or approved discount amount was not saved. Hence, we are enhancing the same, similar to the principal field, to track the discount amount entered at each stage

FINERACT-2455

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