Update monitoring settings

Partial upsert. screenshotIntervalSeconds must be 60-1800. consentAt is stamped the first time either capture channel is enabled.

curl -X PUT "https://example.com/v1/monitoring/settings" \  -H "Content-Type: application/json" \  -d '{}'

{  "settings": {    "screenshotsEnabled": true,    "screenshotIntervalSeconds": 0,    "activityEnabled": true,    "consentAt": "2019-08-24T14:15:22Z"  }}