FINERACT-2576: Add unit test for MoneyTest in fineract-core

[paultofunmi]

Description

This PR adds a comprehensive MoneyTest suite covering all major operations on the Money class, including parameterized edge cases for floating-point precision.

Test coverage added:

• plus(double) — parameterized cases including negative values and floating-point precision edge cases
• total(Money...) varargs — aggregation of multiple Money instances, and exception thrown on empty input
• total(Iterable<Money>) — iterable aggregation including single-element and empty-list exception cases
• roundToMultiplesOf(double, int) — parameterized cases plus NaN return for negative values
• roundToMultiplesOf(BigDecimal, Integer) — parameterized cases including zero and negative multiples
• roundToMultiplesOf(Money, int) — with and without MathContext, including zero-multiple passthrough
• ceiling(double, double) — NaN cases and valid cases covering zero, exact multiples, and rounding up
• floor(double, double) — NaN cases and valid cases covering negative step sizes and floating-point steps
• getAmountDefaultedToNullIfZero() — null for zero, non-null with correct value for non-zero
• dividedBy(BigDecimal/double/long) — identity optimisation (returns same instance when dividing by 1), correct results for division by 2
• multipliedBy(BigDecimal/double/long) — with and without MathContext, identity optimisation for multiplier of 1
• multiplyRetainScale(BigDecimal/double) — scale preservation at currency decimal places
• percentageOf(BigDecimal) — 50%, 100%, and 0% cases
• negated() — positive, negative, and zero (returns same instance for zero)
• abs() — positive, negative, zero, and with MathContext
• zero() — instance method with and without MathContext
• getMc() — non-null MathContext assertion
• copy() — value equality, same currency, different instance; copy with BigDecimal and double overrides

All tests are pure unit tests with no Spring context or database dependencies.

Fixes: https://issues.apache.org/jira/browse/FINERACT-2576

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[Aman-Mittal]

LGTM, only unit tests are added.

[budaidev]

LGTM

[Aman-Mittal]

@adamsaghy can you look at this PR. Me and attilia have given our reviews.