We decided to send 4xx errors to sentry from the FE, except for
ForbiddenErrors.
In some cases, we also need not to send to sentry some 4xx errors, like
user input error, because the error stemming from the user input is
unpredictable (ex: duplicate entry for a record with unicity
constraints) and thus acceptable.
Let's add a isExpected extension on UserInputErrors to introduce a
specific behaviour for them (do not send to sentry).
