Add an intro on data exceptions

Author: NataliaIvakina

modules/ROOT/pages/errors/gql-errors.adoc

@@ -102,7 +102,8 @@ Status description:: error: connection exception - no such routing policy. Polic
 [[_data-exceptions]]
 == Data exceptions
 
-The following is a list of the data exceptions that can occur in Neo4j.
+Database exceptions occur when a client request contains the wrong format, types, or other unsupported input.
+Some examples are data and constraint creation, which conflicts with existing constraints, properties of non-storable type, and spatial and temporal values with invalid components.
 
 === 22N00