A single sec-group-broker-filter instance filters multiple brokers

[gberche-orange]

As a sec-group-filter operator, in order to save RAM when deploying the sec-group-filter on a large catalog (200+ services), I would like to have sec-group-filter apps filter multiple brokers (e.g. all brokers provided by a given service provider team).

See https://github.com/orange-cloudfoundry/sec-group-broker-filter/blob/master/README.md#can-a-single-sec-group-broker-filter-proxy-multiple-upstream-brokers-

The sec-group-filter would expose a route per filtered service, as to allow registration of each filter with the cloudcontroller.

The configuration syntax to list multiple brokers could be similar to the https://github.com/orange-cloudfoundry/static-creds-broker/blob/master/README.md#usage-overview such as:

    BROKER_FILTER[ROUTE1]_URL: 
    BROKER_FILTER[ROUTE1]_USER: 
    BROKER_FILTER[ROUTE1]_PASSWORD: 

    BROKER_FILTER[ROUTE2]_URL: 
    BROKER_FILTER[ROUTE2]_USER: 
    BROKER_FILTER[ROUTE2]_PASSWORD: