Mike Fleetwood authored Dec 31, 2015 and Curtis Gedak committed Jan 29, 2016

At the moment any messages for an encrypted file system aren't shown,
only messages from the outer PartitionLUKS object are shown.  Also in
Win_GParted::activate_paste() the selected Partition object, possibly
a derived PartitionLUKS, is cloned and the messages cleared.

Therefore a set of accessor methods must be provided to query and modify
partition messages.  Messages will be stored in the Partition object to
which they are added and retrieved from all.  So in the case of a
derived PartitionLUKS they will be retrieved from the messages vector of
the PartitionLUKS object itself and the messages vector for the
encrypted file system it contains.

To replace code like this in GParted_Core:

    partition_temp->messages = messages;

We might naturally provide a set_messages() method which assigns the
messages vector and is used like this:

    partition_temp->set_messages( messages );

However on a PartitionLUKS object what should set_messages() do?  By the
name it will replace any existing messages in the PartitionLUKS object
itself, but what should happen to the messages for the contained
encrypted Partition object?  Should they be cleared or left alone?
Rather than implement set_messages() with unclear semantics implement
append_messages(), which in the PartitionLUKS object case will clearly
leave any messages for the contained encrypted Partition object alone.
Append_messages() is then used to add messages as the Partition or
PartitionLUKS objects when populating the data in GParted_Core.

Bug 760080 - Implement read-only LUKS support