Add isReadable method to UnwrappedMongoPersistentProperty.

Closes: #4489

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/UnwrappedMongoPersistentProperty.java

@@ -255,6 +255,11 @@ class UnwrappedMongoPersistentProperty implements MongoPersistentProperty {
 		return delegate.isWritable();
 	}
 
+	@Override
+	public boolean isReadable() {
+		return delegate.isReadable();
+	}
+
 	@Override
 	public boolean isImmutable() {
 		return delegate.isImmutable();