Context: There is a section in deployments configuration that allows to put custom rclone credentials.

I think we should move this section to the linked services (profile section).
The idea is that you would manually create the linked storage in Profile section and the deployment configuration should only show the dropdown with the available linked storages (but no longer the manual option).

Doing it like that has the benefit that you don't need to manually add the storage every time you make a new deployment: it's already saved in the linked storages section.

For extra points, we can leverage PAPI /storage routes to check that the new storage is valid. The workflow would be:

1. User enters rclone credentials into Dashboard,
2. Dashboard saves rclone credentials into Vault,
3. Dashboard calls PAPI storage_ls endpoint with that storage provider,
   4.1 If the call is successful, great: the new storage has been created
   4.2 If the call fails, Dashboard deletes rclone credentials from Vault and message is show to users: "new storage could not be validated"