Server provide API key management

Currently there is an issue with Hetzner API token usage for servers, although it may be applicable to other server providers.

Hetzner API tokens are bound to Hetzner projects. After moving some servers to a different project, the API token used to create them is no longer usable for these servers, which means Ploi will be unable to delete the servers via API after these are deleted from the panel.

Currently there is no way to specify which API token must be used for a server. The server provider assigned to a Ploi team is also ignored.

The fix would be to allow the user to specify which API token must be used for managing the server.