action and @action do not work in 0.28.0

[rjmatthews62]

I have recently upgraded from RN0.73 to RN0.79, and also moved to @nozbe/watermelondb@0.28.0
This resulted in the application failing with some not very meaningful error messages.
Because this happens quite early in the startup process (in index.js) the RN debugger was not properly loading the source files, which made tracking difficult.
The short answer seems to be that @action is not supported any more, and needs to be replaced with either @reader or @writer.
Ditto the "Database.action" method is "not found" at runtime.
Again, replace with either reader or writer as appropriate.

This took me a while to work out, especially as "action" is still defined in @nozbe/watermelondb/Database/index.d.ts but NOT in index.js.

Hoping this will be useful to someone.