how to add custom code in sample?

[sjvans]

i think we need guidance for this

i see two options:

1. server.js
2. cds-plugin.js + dev dep to self

i prefer option 2. as it would, in theory, allow to require the sample in another sample (e.g., "mashup")

[nkaputnik]

I think using cds-plugin.js is the more elegant solution, but needs to be documented better for unsupsecting developers

[sjvans]

current "state of the art" in notifications sample: https://github.com/cap-js/calesi/blob/f0cda78d7b17d218b14f25bc9a760658bce66507/samples/notifications/srv/server.js