Location: disallow move based on purpose

The `posix_move` should not be always allowed for certain locations. This
commit ensures that it's not used when the original location is backlog or
AIP storage.

This is connected to archivematica/Issues#270.

storage_service/locations/api/resources.py

@@ -372,6 +372,10 @@ def _move_files_between_locations(self, files, origin_location, destination_loca
                 destination_location.relative_path, destination_path)
 
             try:
+                if origin_location.is_move_allowed():
+                    LOGGER.debug(
+                        'Moving files from this location is not allowed')
+                    raise PosixMoveUnsupportedError
                 origin_space.posix_move(
                     source_path=source_path,
                     destination_path=destination_path,

storage_service/locations/models/location.py

@@ -41,6 +41,12 @@ class Location(models.Model):
     TRANSFER_SOURCE = 'TS'
     REPLICATOR = 'RP'
 
+    # List of purposes where
+    PURPOSES_DISALLOWED_MOVE = (
+        BACKLOG,
+        AIP_STORAGE,
+    )
+
     PURPOSE_CHOICES = (
         (AIP_RECOVERY, _('AIP Recovery')),
         (AIP_STORAGE, _('AIP Storage')),
@@ -133,6 +139,10 @@ def get_description(self):
         """ Returns a user-friendly description (or the path). """
         return self.description or self.full_path
 
+    def is_move_allowed(self):
+        """Returns whether it's allowed to move contents from this location."""
+        return self.purpose not in self.PURPOSES_DISALLOWED_MOVE
+
 
 @receiver(models.signals.pre_delete, sender=Location)
 def unset_default_location(sender, instance, using, **kwargs):