Token-based probe adoption

[MartinKolarik]

An alternative adoption flow, where a user can set an env var like GLOBALPING_OWNER= on the probe to adopt it with no further interaction required. The value is a special adoption token (visible in dashboard). All "start a probe" instructions in dashboard/main website will (optionally, with a toggle) include the token in the command so that newly started probes are automatically adopted.

Now

1. In Directus, add an adoption_token attribute for each user. It'll be stored in plain text and can be regenerated by the user.
2. On the probe, read GLOBALPING_OWNER and pass it to the API.
3. On the API:
   3.1. If the probe is already adopted (matched by IP/alt IP/UUID):
   3.3.1. If the owner matches the token - no action needed.
   3.3.2. If the owner is different - delete the existing adoption and create a new one based on the token, send a notification to both accounts.
   3.2. If the probe is not adopted - adopt it. Send a notification.

TBD: how does the dashboard detect newly adopted probes to show to the user in the "verify" step? The most reliable way might be adding a new entity like gp_adopted_probes_notifications where a record is created by the API and deleted by the dashboard once the user clicks "finish".

Later - pending design

Update all adoption instructions and add a way to regenerate the token. See the updated flow here: https://docs.google.com/document/d/1lXgfDFXIWQe-VHYgIkZwKCLw_86jzhoMubomPpJVmOQ/edit?usp=sharing