Feed update clobbers changes to feed title

[twm]

The management UI exposes the feed title as an editable field, but if you change it it just gets clobbered on the next update.

[radiac]

That's a good point. It updates in case the author changes their feed title, but there's currently no way to tell whether the feed author or the yarr user changed it. We could fix this with a custom_title field - either an internal BooleanField to lock the title if the user changes it, or another TextField for a custom title which overrides the one from the feed.

The second TextField would let us keep the official feed title, but then again I'm not sure when we'd ever use it - we shouldn't overwrite the user's custom title, even if the feed title changes.

I'm therefore leaning towards a custom_title BooleanField; if we ever find a use for the official feed title, we could always do a simple datamigration at that point. I'll implement this in a few days if there's no further discussion.

[twm]

I think that it would be useful to maintain both of them as separate fields, since two fields will be necessary in any case. The feed title as of last update can be shown on the feed's management page alongside last updatetime, etc. The separate fields also map nicely onto OPML's title and text attributes.