Rules for using an electronic text as the texbook for a class
Well .. one idea is to assign the book as the textbook then notify the students that they should get the book via buying from amazon ... or that your library has access to Springer resources free of charge for the students. University students are adults that can make their own decisions.

As the course coordinator you are not selling the book, and it is not your responsibility to hand in a book to each student. Students can: buy the book or use free resources on their own progeratives. Students are not liable, since they are just accessing your library to view already available resources.

As long as you do not directly post content such as homework questions or chapter text from the book or directly share such content in any way, such as on the course website or as handouts, you are not liable. You are just assigning a book as recommended textbook and notifying the students their options. Students are also not liable since your library enables them to access free material they wish to view.

I also just want to give an example of clear violation. If you buy the book and make a pdf out of it and share them in course site (does not matter whether public access or not) that would be a breach of copyright.