fix(rest): avoid NPE in obligation Boolean filter

[YianZhao]

Closes: #3881

Summary

This PR fixes a possible NullPointerException in RestControllerHelper#getObligationIdsFromRequestWithValueTrue(...).

The previous implementation used:
reqBodyMap.getValue().equals(true)
which could throw an NPE if the map contained a null value.

Changes made

• Replaced the Boolean check with Boolean.TRUE.equals(...)
• Simplified the stream pipeline to directly collect matching keys into a Set

Before
.filter(reqBodyMap -> reqBodyMap.getValue().equals(true))

After
.filter(entry -> Boolean.TRUE.equals(entry.getValue()))

Result

• Prevents NPE for null Boolean values
• Keeps the intended behavior of returning only keys with value true