1d interval not supported by Kennel, 24h interval not supported by Datadog

[aglover-zendesk]

It looks like Datadog changed some of the interval syntax in their API. When I generate a new monitor via the UI with an evaluation period of 1 day, the query I get in the export is

"query": "sum(last_1d):min:...

When I execute this in Kennel, Kennel raises an error that my interval is invalid (see https://github.com/grosser/kennel/blob/master/lib/kennel/models/monitor.rb#L158-L163).

If I try to change this to 24h, Kennel doesn't raise an exception but Datadog chokes on the request:

Error 400 during PUT /api/v1/monitor/5315705
request:
...
"query": "sum(last_24h):min:...
...
response:
{"errors":["The value provided for parameter 'query' is invalid"]}

Guessing we need to allow 1d as a valid interval

[grosser]

and remove 24h ?