DeleteAsync behaves inconsistently

[achilles-portarinos]

currently the behaviour for DeleteAsync is inconsistent,

Actual behaviour

• DeleteAsync(id) does not throw whereas
• DeleteAsync(id, partitionKey) throws.

Expected behaviour:

• All precise DeleteAsync methods have the same behaviour when the entity under deletion is not found. The behaviour should be to throw, since it corresponds to a precise lookup.
• DeleteAsync via predicate should not change behaviour, it should not throw, since it is an imprecise lookup. It can delete multiple entities or none. It should however return the number of items that get deleted.
• The XML documentation of the IDatabaseRepository interface should be updated.
• There will be no flag to control the throwing of exception on deletion. Precise deletions throw, imprecise do not throw.

[achilles-portarinos]

During discussion, we identified that soft-delete is not fully implemented. The Issue description has been updated to reflect the expected behaviour.