Make cloud cost query aggregator required (#3318)

This is required by the API, so the documentation is currently
confusing.

Author: fpighi

datadog/resource_datadog_monitor.go

@@ -581,7 +581,7 @@ func getMonitorFormulaQuerySchema() *schema.Schema {
 							},
 							"aggregator": {
 								Type:             schema.TypeString,
-								Optional:         true,
+								Required:         true,
 								ValidateDiagFunc: validators.ValidateEnumValue(datadogV1.NewMonitorFormulaAndFunctionCostAggregatorFromValue),
 								Description:      "The aggregation methods available for cloud cost queries.",
 							},

docs/resources/monitor.md

@@ -166,14 +166,11 @@ Optional:
 
 Required:
 
+- `aggregator` (String) The aggregation methods available for cloud cost queries. Valid values are `avg`, `sum`, `max`, `min`, `last`, `area`, `l2norm`, `percentile`, `stddev`.
 - `data_source` (String) The data source for cloud cost queries. Valid values are `metrics`, `cloud_cost`, `datadog_usage`.
 - `name` (String) The name of the query for use in formulas.
 - `query` (String) The cloud cost query definition.
 
-Optional:
-
-- `aggregator` (String) The aggregation methods available for cloud cost queries. Valid values are `avg`, `sum`, `max`, `min`, `last`, `area`, `l2norm`, `percentile`, `stddev`.
-
 
 <a id="nestedblock--variables--event_query"></a>
 ### Nested Schema for `variables.event_query`