Returns complete list of vendors provided in the given credentials

List can be filtered by optional query parameters:

• seat ID - internal seat identifier assigned to vendors. Useful when vendor list must be narrowed down and displayed for the specific seat only (please see /venues/{venue_id}/levels/{level_id}/seats endpoint for complete list of seat IDs)
• venue ID - internal venue identifier associated with vendors. Since the complete list contains all venues/vendors provided in the credentials this filter could be used when vendor list must be retrieved for specific venue only
• external ID - external identifier assigned to vendors
• include all vendors - boolean flag, true - ALL vendors are returned, false returns a list of mobile vendors only, default value is false