[Dbix-class] Encapsulate multiple steps for insertion

[Tobias]

> You might consider whether splitting this table was a premature
> optimization.  I can't know if it is, it's really up to you, but it's
> often the case (especially with forum posts, as the most typical
> pattern will be to insert the data once and then read-only from there
> out, with only a small fraction of the texts being updated by later
> edits, and even then very few times).

To be honest I'm dealing with a legacy database schema which is currently
serving approximately 30 million page impressions/month and 12.000 posts/day
and I don't want to change it because it performs really well. I took a look
into other successful high-volume forum applications like vbulletin and phpbb
and they all spin off the message texts from the post entries. I suppose they
know what they're doing ...

--Tobias