Do not automatically restore sharded datasets

In the case of partitioned datasets, the application layer is
responsible for data management, not float.

docs/configuration.md

@@ -495,6 +495,12 @@ attribute.
 *master_election* attribute is also true, the backup job will only be
 run on the master host for the service.
 
+`sharded`: When this attribute is true, the dataset is considered a
+sharded (partitioned) dataset, so float will **not** automatically
+attempt to restore it on new servers: the idea is that for sharded
+datasets, the application layer is responsible for data management.
+This attribute is false by default.
+
 `owner`: For filesystem paths, the user that will own the files upon
 restore.
 

roles/base/tasks/backup_dataset.yml

@@ -11,7 +11,7 @@
     dataset_owner: "{{ item.1.get('owner', '') }}"
     dataset_path: "{{ item.1.get('path', '') }}"
     dataset_type: "{% if 'backup_command' in item.1 %}pipe{% else %}file{% endif %}"
-    dataset_should_backup: "{{ item.0.name in float_enabled_services and ((not item.1.get('on_master_only', False)) or (item.0.get('master_host') == inventory_hostname)) }}"
+    dataset_should_backup: "{{ (item.0.name in float_enabled_services) and (not item.1.get('sharded', False)) and ((not item.1.get('on_master_only', False)) or (item.0.get('master_host') == inventory_hostname)) }}"
 
 - name: Set up configuration for dataset {{ dataset.name }} (source)
   template: