Improve Payutc login

[abrasseu]

Currently, to login and add an item to Payutc, the API gets credentials from its settings:

PAYUTC = {
    # Application key login OK
    'app_key': env.str("PAYUTC_APP_KEY"),
    # User login NOT OK
    'mail': env.str("PAYUTC_MAIL", validate=[Email()]),
    'password': env.str("PAYUTC_PASSWORD"),
}

It should login the current user to Payutc instead and not a admin user from the config.
We should also add a Sync to Payment Service button on the UI.