Add GET method for TriggerCollection

Added GET method for retrieving list of Triggers from Telemetry service

Tested:
- Added single Trigger and requested result from bmcweb via
  /redfish/v1/TelemetryService/Triggers
- Added multiple Triggers numeric and discrete, and requested results
  from bmcweb via /redfish/v1/TelemetryService/Triggers
- Verified uri /redfish/v1/TelemetryService/Triggers by using
  Redfish-Service-Validator with no Triggers/empty Collection (passed)

Signed-off-by: Lukasz Kazmierczak <lukasz.kazmierczak@intel.com>
Change-Id: Ide00eb44901ea1b97b80fc5c5ddfd97e393d4a04
diff --git a/redfish-core/lib/telemetry_service.hpp b/redfish-core/lib/telemetry_service.hpp
index 8ecc591..b79a5cd 100644
--- a/redfish-core/lib/telemetry_service.hpp
+++ b/redfish-core/lib/telemetry_service.hpp
@@ -23,6 +23,8 @@
         "/redfish/v1/TelemetryService/MetricReportDefinitions";
     asyncResp->res.jsonValue["MetricReports"]["@odata.id"] =
         "/redfish/v1/TelemetryService/MetricReports";
+    asyncResp->res.jsonValue["Triggers"]["@odata.id"] =
+        "/redfish/v1/TelemetryService/Triggers";
 
     crow::connections::systemBus->async_method_call(
         [asyncResp](const boost::system::error_code ec,