Hard-coded salt

[igormukhingmailcom]

Hard-coded salt:
https://github.com/userbase-project/userbase-client-php/blob/master/src/User.php#L37

We need leave it empty and throw exception if it not provided.

[h-wang]

@igormukhingmailcom totally agree. We should configure it in parameters.yml probably.
@igormukhingmailcom can you work on it? thanks.

[igormukhingmailcom]

@h-wang I'm planning to upgrade this lib too :)

[h-wang]

@igormukhingmailcom thanks 👍