Display how long is the waiting list

When a document has a waiting list, we should display (both frontsite and backoffice) how many people is waiting for the book

Notifications: patron requests a loan with no copies available at the library (on loan): can we write You are the X in the waiting list? without taking into account the period of interest... If yes, change email templates.

Start by locating the waiting-list displays in the frontsite and backoffice, then find the notification email templates for loan requests when no copies are available. Confirm how the waiting position is calculated and verify that the displayed count and email wording match the requested behavior.

Written by the indexing model from the issue text.