In order to allow public access to the graph API, we need to prevent
users to DoS the graph service with resource intensive queries.
Fortunately, the graph API supports a max_edges parameter to limit the
number of edges traversed by the graph.
According to the type of user querying the graph service through the
Web API proxy, a maximum value for the max_edges will be set before
sending a request to the graph API.
Three type of users are considered: anonymous, standard and staff.
The maximum values for the max_edges query parameter according to
user types are retrieved from the webapp configuration.
Related to T3836