Add a `key` option to mutations that is optional

[posva]

This will allow later on to retrieve mutation state, cancel ongoing mutations etc. By default mutations have no key and cannot be "reused"

[ElisePatrikainen]

Should the mutation key option have the same type as the query key option (apart from the fact it is optional)? If yes, should we create a mutualized type (UseKey for example, which would be used for mutation and query keys)?

[posva]

yeah, it could be mutualized into an EntryKey

[ElisePatrikainen]

Ok, thank you.