api2/tape/backup: add 'force-media-set' parameter to manual backup

so that a user can force a new media set, e.g. if he uses the
allocation policy 'continue', but wants to manually start a new
media-set.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

src/tape/pool_writer/mod.rs

@@ -71,11 +71,12 @@ impl PoolWriter {
         drive_name: &str,
         worker: &WorkerTask,
         notify_email: Option<String>,
+        force_media_set: bool,
     ) -> Result<Self, Error> {
 
         let current_time = proxmox::tools::time::epoch_i64();
 
-        let new_media_set_reason = pool.start_write_session(current_time)?;
+        let new_media_set_reason = pool.start_write_session(current_time, force_media_set)?;
         if let Some(reason) = new_media_set_reason {
             task_log!(
                 worker,