Add an error mailer

[geourjoa]

We want to known and debug error occuring in MMU.

To start we will focus on backend error.

All the 500 like error must be handle and send to arvest@tetras-libre.fr

At least we want the following information :

• Stack trace : what caused the error
• User causing the error
• Requested API route and param of the request
• Error timestamp on server (to search easily in the log)

[geourjoa]

@daxid Something to add ?

[daxid]

it seems good to me.