Introduce Translated Data Exceptions

It is very useful to introduce translated exceptions such as DuplicateKeyException. This is nice for spotting some edge cases. We are using it to display some error messages to user.

The issue names no files, tests, or entry points. Start by locating the existing data exception handling and clarify which translated exceptions are required, including DuplicateKeyException and the intended user-facing messages. Done should mean the agreed exception types are introduced and their edge cases are covered by tests.

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