[BUG] Non-serializable operation and reference value in BooleanOperator

[holtvogt]

Circumstances
Currently, the generic types operation and reference value are non-serializable.

Seen in:

meet-eat-data/src/main/java/meet_eat/data/predicate/BooleanOperator.java

Line 20 in 2ae1008

private final T operation;

meet-eat-data/src/main/java/meet_eat/data/predicate/BooleanOperator.java

Line 22 in 2ae1008

private final S referenceValue;

Expected behavior
The operation and reference value must be serializable.