Added validation for connection_type

Author: kumar-avijit

sumologic/resource_sumologic_monitors_library_monitor.go

@@ -149,6 +149,7 @@ func resourceSumologicMonitorsLibraryMonitor() *schema.Resource {
 										Type:     schema.TypeString,
 										Optional: true,
 										Computed: true,
+										ValidateFunc: validation.StringInSlice([]string{"Email","AWSLambda","AzureFunctions","Datadog","HipChat","Jira","NewRelic","Opsgenie","PagerDuty","Slack","MicrosoftTeams","Webhook"}, false),
 									},
 									"subject": {
 										Type:     schema.TypeString,