RequiredMappingStrategy
Defines the strategy used when emitting warnings for unmapped members.
Both = -1
Warnings are emitted for both unmapped source and target members.
None = 0
Warnings are not emitted for unmapped source or target members.
Source = 1
Warnings are emitted for unmapped source members but not for target members.
Target = 2
Warnings are emitted for unmapped target members but not for source members.