Duplicate Key: Add key to log message

Currently, when importing on a connector, Identity Broker will generate a duplicate key error when it encounters multiple records that have the same key. This is problematic in itself, but is exacerbated because IdB apparently drops the whole page (~1000 records) when this occurs.

The error presented is something like this:
System.ArgumentException: An item with the same key has already been added.

Given that the impact of having a single duplicate record is quite high (1000 records not imported!), it's important to find these duplicate records in the end source and to either eradicate them, or select a more appropriate key value. To this end, I request an improvement for IdB to display the duplicate key in the error message when the error is thrown. Eg,

System.ArgumentException: An item with the same key (12345) has already been added.

Or perhaps even go so far as to include the attribute(s) used in the key:

System.ArgumentException: An item with the same key (entityID:12345) has already been added.
or (in the case of multiple attribute keys
System.ArgumentException: An item with the same key - (entityID,12345):(locationID,123) - has already been added.