"Port" the unique rule from Eve?

[funkyfuture]

we should do that, or shouldn't we?

i can think of two different semantics atm:

• simply that any container like lists can contain only one instance of a value
• the more tricky one where a sequence of mappings must not have one value assigned to the same field among these mappings

maybe that would be two different rules to avoid ambiguity and to keep the code straight-forward.

the Cerberus implementation should hence be capable to solve Eve's limitation of not detecting duplicates in a payload. while Eve would need to extend it with regards to the database collection.

[nicolaiarocci]

Of course I'd like this 😃 I also agree on having two different rules: they solve (not-so-)slightly different problems.

[funkyfuture]

closing this issue as there are currently no intentions to continue a next major release.