[communication] fix endpoint env var name (Azure#18138)

* fix endpoint env var name

* add COMMUNICATION_ACCESS_KEY env var

* change key1 to primaryKey

Author: 0rland0Wats0n

sdk/communication/test-resources.json

@@ -50,10 +50,14 @@
             "type": "string",
             "value": "[listKeys(resourceId('Microsoft.Communication/CommunicationServices',variables('uniqueSubDomainName')), '2020-08-20-preview').primaryConnectionString]"
         },
-        "COMMUNICATION_ENDPOINT_STRING": {
+        "COMMUNICATION_ENDPOINT": {
             "type": "string",
             "value": "[concat('https://', parameters('baseName'), '-', parameters('endpointPrefix'), '.communication.azure.com')]"
         },
+        "COMMUNICATION_ACCESS_KEY": {
+            "type": "string",
+            "value": "[listKeys(resourceId('Microsoft.Communication/CommunicationServices',variables('uniqueSubDomainName')), '2020-08-20-preview').primaryKey]"
+        },
         "RESOURCE_GROUP_NAME": {
             "type": "string",
             "value": "[resourceGroup().Name]"