Check in a book

As a dwyler
Once I have finished with a book from the library, I would like to be able to return it and mark it as checked in,
So that I am no longer responsible for the book.

## Acceptance criteria
+ I can search for my book and see a 'Check in' or 'Return book' button (instead of check out)
+ I can click on the button and have this book marked as checked in
+ _Only_ the dwyler that checked out the book and admin can mark a book as checked in
+ The book now appears on searches for books as available