Feature: Add ability to de-duplicate on multiple fields

[luke-hill]

Currently de-duplication is only performed on the primary key
We should allow on a model basis to perform multiple uniqueness checks

Use cases

• When secondary attribute is found used, we warn
  • We can either update in place or not, dependent on desired outcome
    • In EO previously, we used to update in place for review dupe to say updated value (This is bad, should use a .find_or_create helper and then call #update
• When secondary attribute is found used, we crash