Updates the alias (display name) of an account held at the provider. Only the alias is sent, and no other account property should be modified.

Business Context: Called whenever an account is renamed in Toqio, whether from the Toqio frontend, the admin portal or the public API, and whether through the dedicated rename action or through a general account edit that changes the alias. Toqio stores the new alias first and then calls this endpoint so that the provider holds the same name.

Important:

• This is the endpoint Toqio calls for alias changes. Renames are never sent through Update account (PUT /customers/{customerId}/clients/{clientId}/accounts/{accountId}).
• The call is not gated by any capability: it is made for accounts of every provider. A connector that does not support renaming accounts should return 500 FUNCTION_NOT_IMPLEMENTED_YET.
• A failure here does not roll back the rename in Toqio: the user keeps seeing the new alias even if the provider rejects it.