`MergingDocument` should override the equals method

[CoolLoong]

Is your feature request related to a problem? Please describe.
MergingDocument should override the equals method

Describe the solution you'd like
add following code to MergingDocument

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            } else if (o instanceof Document document) {
                return this.entrySet().equals(document.entrySet());
            } else {
                return false;
            }
        }

Describe alternatives you've considered

Additional context