See this topic for breaking changes in 1.19.0 https://community.nodebb.org/post/86172. You can rename middleware.authenticateOrGuest to middleware.authenticateRequest

It should cache for an hour, I think (based on a quick look at nodebb package manager code). So yes - you have to wait a bit before the nbbpm refreshes. You can just install the updated version manually by using npm install <package name> from the command line in NodeBB folder.

Thank you very much @oplik0 for your very detailed and helpful answer. 👍 I will take a look into the write-api plugin first and see how far I get. From your description it sounds like what I need.