Merge branch 'warning-preferences' into 'master'

[Docs] Add warning related to #12

See merge request !15

docs/admin/10_configuration.rst

@@ -58,3 +58,9 @@ Details of the synchronization can be customized with the remaining config optio
 * **Power level for owners**: Specifies the Matrix room power level for group owners.
 * **Power level for members**: Specifies the Matrix room power level for group members.
 * **Reduce existing power levels**: For existing Matrix rooms that are going to be managed by AlekSIS, power levels can be overwritten by AlekSIS to match the previously defined power levels.
+
+.. warning::
+    Do not change the **Use Spaces** preference after provisioning any rooms
+    for groups with sub-groups. If you need to change the behaviour after
+    the initial provisioning, first unlink the rooms and sketch out a manual
+    migration plan!