Issue Summary

When creating a Zabbix integration using the Integration API, sendViaOEC or sendViaMarid are flagged as required fields by default. These should only be needed if "Send Alert Actions to Zabbix" is enabled. 

Steps to Reproduce

1. Send a request to the integration API to create a new Zabbix integration using only the mandatory fields: 

   curl -X POST 'https://api.opsgenie.com/v2/integrations' -H 'Authorization: GenieKey XXXX' -H 'Content-type: application/json' -d 
   '{ 
       "name":"zabbix-integration-api", 
       "type":"Zabbix" 
   }'

Expected Results

Zabbix integration is created.

Actual Results

Response for the above request --->

{
"message":"Either sendViaOEC or sendViaMarid should be selected.",
"took":0.013,
"requestId":"e4b316d0-6d77-4f2c-98c6-c3fb1a50a52c"
}  

Workaround

Explicitly include the field sendAlertActions:false in your create integration request: 

curl -X POST 'https://api.opsgenie.com/v2/integrations' -H 'Authorization: GenieKey XXXXX' -H 'Content-type: application/json' -d
'{
 "name":"zabbix-integration-api",
 "type":"Zabbix",
 "sendAlertActions":false
}'