corpus name needs to be unique across different users

[carinedengler]

Describe the bug

adding a new corpus with the name new as user foo is not possible if user bar already has a corpus with such a name, leading to the following error message

You have already a corpus going by the name corpus

even if the user foo does not have any corpora associated with them at all

To Reproduce
Steps to reproduce the behavior:

1. add user foo
2. add user bar
3. add corpus with name new as user bar
4. try to add corpus with name new as user foo

Expected behavior
a user should be able to add a corpus with a name which is already in use by a corpus of another user

[PonteIneptique]

You're totally right, we should probably add the creator name in a secondary field, or it's ID (which would make sense to be honnest)

However, as you can share corpora, you could find yourself in a situation where a user have access to identically named corpora. So on the front, we should recoved and show this when a user have two corpora with the same name (not always, that would be clunky ?)