A user in Slack was having issues processing reports due to the config_version field containing values that exceeded the size of a varchar 255. It turned out that their report configuration_version was longer than 255 characters because it included git messages and links, which they were rendering in puppetboard as clickable commit messages back to github.
I don't see a reason for the character limit and the usecase seems interesting - we should just drop it.
We should do the same for containing_class, since we already use text for resource titles and these can get long as well. I think with puppet_version we're probably safe for now.
Edit: Really we should consider whether we need varchars for anything at this point. None of our varchar columns are enforcing any kind of correctness rules and postgres won't make a distinction from a storage space perspective as far as I know. file paths are also limited in PDB to 1024 characters, which is not technically sound either.