Add comment to work item together with information about the sender

[hendrikmaarand]

This introduces two new special values (##MessageLastReply and ##MessageLastReplyWithSender) and a new configuration option DefaultFieldValuesOnUpdate. DefaultFieldValuesOnUpdate is same as DefaultFieldValues except that its default values are used when an update is applied to a work item. ##MessageLastReplyWithSender allows to set the default value for field History similarly as is currently done for Description with ##MessageBodyWithSender.

This change also unifies the code a bit as we do not need to have special cases for History field.

It should also allow to remove the configuration option OverrideChangedBy and replace it with ##Sender as default value for 'Changed By' on update.

[hershi]

First off - sorry for the very long delay in reviewing it.

Overall, the change looks good - thanks for taking the time to make it. The one concern I have is that it would break any existing setup out of the box, and would require an update to all the configs to make sure that update messages are indeed properly adding the last message to the history.
My suggestion is to change the default behavior such when the relevant config section is missing (i.e. when DefaultFieldValuesOnUpdate is an empty list or null), it works the same way as the legacy code.

The rest of it looks good, and I like the further simplification of the code (no special handling of History field) - it definitely yields a nicer abstraction and more flexible behavior

[hendrikmaarand]

Your concern seems valid. Our Mail2Bug set up had a base template from which we generated all the instance configurations. That is why the issue probably did not occur to me as this kind of configuration change only required a simple change to the base template.

Regarding the proposed changes, the problem for me is that I do not have the development/testing environment for this anymore and I am not too inclined to set something up. Maybe this change can then just wait for some bigger release.

[hershi]

No worries Hendrik. I'll try to take a look once I have some time and see if I can add my suggestion to the code you created and then commit