simple CRUD interface to show/add/edit/delete metric servers
it's a bit different from PVE's so it's harder to reuse that than to
copy it. If we need it again, we can still refactor and combine them.
introduce 'PBS.Schema' class to hold the server type/xtype mappings
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
