[admin] Dump logs may be too long

[sveetch]

Is your feature request related to a problem? Please describe.

Dump detail view in admin shows the logs from dump creation. They can quickly becomes too long because of storages files.

Describe the solution you'd like

The logs should not be included in the admin detail view anymore, instead it should be a link to a very basic plain text view that will just return the logs. Obviously this is a view that will be wired into the admin alike the download view, so it is well protected.

Describe alternatives you've considered

We could up the logging level from DEBUG to INFO but it would be less useful logs.