Be able to logout from providers

[DevGiuDev]

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Describe the bug
Once you login to a provider there is not way for ECA to forgot about the models discovered. Could be interesting a /logout command to remove this data

To Reproduce
Steps to reproduce the behavior:

1. Login to provider
2. There is no way to remove this models unless you delete directly from ~/.cache/eca/db.transit.json

[ericdallo]

This is already possible from some time