feat(dashboard): use INHERIT period by default (#108)

We should set INHERIT by default to ensure that every graph has the preferred time resolution instead of the AUTO one (which can be 5m or 1h based on the range). It is better to have it set like this, since it will better correspond to alarms.

---

_By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license_

Author: voho

API.md

@@ -24037,7 +24037,7 @@ public readonly detailDashboardPeriodOverride: PeriodOverride;
 ```
 
 - *Type:* aws-cdk-lib.aws_cloudwatch.PeriodOverride
-- *Default:* automatic (period dependent)
+- *Default:* respect individual graphs (PeriodOverride.INHERIT)
 
 Period override for the detail dashboard (and other auxiliary dashboards).
 
@@ -24065,7 +24065,7 @@ public readonly summaryDashboardPeriodOverride: PeriodOverride;
 ```
 
 - *Type:* aws-cdk-lib.aws_cloudwatch.PeriodOverride
-- *Default:* automatic (period dependent)
+- *Default:* respect individual graphs (PeriodOverride.INHERIT)
 
 Period override for the summary dashboard.
 

lib/dashboard/DefaultDashboardFactory.ts

@@ -42,7 +42,7 @@ export interface MonitoringDashboardsProps {
   readonly detailDashboardRange?: Duration;
   /**
    * Period override for the detail dashboard (and other auxiliary dashboards).
-   * @default automatic (period dependent)
+   * @default respect individual graphs (PeriodOverride.INHERIT)
    */
   readonly detailDashboardPeriodOverride?: PeriodOverride;
   /**
@@ -52,7 +52,7 @@ export interface MonitoringDashboardsProps {
   readonly summaryDashboardRange?: Duration;
   /**
    * Period override for the summary dashboard.
-   * @default automatic (period dependent)
+   * @default respect individual graphs (PeriodOverride.INHERIT)
    */
   readonly summaryDashboardPeriodOverride?: PeriodOverride;
   /**
@@ -102,7 +102,8 @@ export class DefaultDashboardFactory
         {
           dashboardName: props.dashboardNamePrefix,
           start: detailStart,
-          periodOverride: props.detailDashboardPeriodOverride,
+          periodOverride:
+            props.detailDashboardPeriodOverride ?? PeriodOverride.INHERIT,
         }
       );
     }
@@ -114,7 +115,8 @@ export class DefaultDashboardFactory
         {
           dashboardName: `${props.dashboardNamePrefix}-Summary`,
           start: summaryStart,
-          periodOverride: props.summaryDashboardPeriodOverride,
+          periodOverride:
+            props.summaryDashboardPeriodOverride ?? PeriodOverride.INHERIT,
         }
       );
     }
@@ -126,7 +128,8 @@ export class DefaultDashboardFactory
         {
           dashboardName: `${props.dashboardNamePrefix}-Alarms`,
           start: detailStart,
-          periodOverride: props.detailDashboardPeriodOverride,
+          periodOverride:
+            props.detailDashboardPeriodOverride ?? PeriodOverride.INHERIT,
         }
       );
     }