Record Change Detection for CMS

[ischommer]

When you have a facility for editing records - such as a CMS or grants processing database - there needs to be some kind of locking facility, so that people don't wind up overwriting other people's changes.

We recommend that this is implemented as a generic locking toolkit, that is first applied to the CMS, then to other edit forms in systems as required.

Note also that Versioned.php makes a call to "SELECT MAX(Version) + 1", which will break if two people are editing the same record at the same time.

[sminnee]

We should merge in the changes in this arena from NZCT - apply r35423 to branches/2.0

[sminnee]

Do we want to implement locking, or just change detection? You know, come back with an error saying "sorry, someone edited this page since you opened it" like a wiki.

Otherwise, I think that we will risk accidentally leaving pages locked when people want to edit them, since we have the page available for editing when it is first viewed in the CMS.

Including OriginalVersion? as a hidden field in the CMS, and checking that before writing, would work.