function that allows searching by provider id in the list of known SDMXServiceProvider. This function can be used for interrogating the list of default providers known by rsdmx, and is used internally by readSDMX
Usage
findSDMXServiceProvider(agencyId)
Arguments
agencyId
an object of class "character" representing a provider identifier
Value
an object of class "SDMXServiceProvider" (or NULL if no matching)