System for saving booking related conversation

[d-tamm]

Would be good to have the possibility to send emails to users from within the booking system.

[d-tamm]

For alpha release it may be enough to quote some notice in the internal booking comment field.

[d-tamm]

Right now, the system encourages the users to use the booking comment field for communication with booking admins.
When an admin receives a new guest booking, they will see eventual comments the guest entered. Also, if the admin chooses to add something to the comment field, this would be visible to the guest in the confirmation mail. But if further on the guest adds more comments, the admin may never see them because the booking is still marked as confirmed.
One way to handle this better could be to allow writing into the comment field for those users whose bookings need confirmation only if there are any unconfirmed resources in the booking. I.e. the field would be readonly if only confirmed posts are in the booking. Alternatively, any change in the comment made by the guest would set the status of the booking to some new "dirty" state so the booking is again marked in the admin interface to be reviewed. Since the status of bookings right now is derived from the status of the included resources, this is not so straightforward and would maybe require a new DB "dirty" field in the bookings table, but it would give more possibilities to positively "misuse" the comment field for communication.
For users who do not need an admin's confirmation for their bookings, we could expect that the comment field is not used for such two-way communication, so no need to write-protect the comment field in that case.