I'd like to manage spreadsheets (uploaded by a client via API) over google engine. I created test spreadsheet extended by functions in .gs script (which works great if I add them via online editor) but I do not know how to apply such a .gs script to every uploaded spreadsheet automatically (possibly via API).
Moreover, I do not want to share this .gs file by publishing it as an extension (because of security policies).
Updated: I also tried copying existing spreadsheet with working gs script and overwriting its spreadsheet data via API (instead of uploading new one) - it's overwritten data successfully but unfortunately lost gs script. Details are described in separate (bounty) question: Custom google app script doesn't work after copying spreadsheet with google java client