Route to get needed KPI for clients

[JulesGresset]

Description
Add the route /kpi/displayKpi with the query param useCase and two options : POS and KDS
Return one single object containing all data separated by the name of the KPI, example :

{
    "ordersInProgress": {...},
    "clientsCount": {...},
}

For the POS useCase :

• ordersInProgress: orders currently open (=not payed yet)
• clientsCount: Clients currently here (only 'sur place' clients)
• averageWaitingTime1h: average waiting time in the last hour
• averageWaitingTime15m: average waiting time in the last 1/4h
• averagePrepTime1h: average preparation time in the last hour
• averagePrepTime15m: average preparation time in the last 1/4h

For the KDS useCase :

• last15mOrders: The numbers of orders sent in the last 1/4h
• clientsCount: Clients currently here (only 'sur place' clients)
• averageWaitingTime1h: average waiting time in the last hour
• averageWaitingTime15m: average waiting time in the last 1/4h
• averagePrepTime1h: average preparation time in the last hour
• averagePrepTime15m: average preparation time in the last 1/4h