Merge branch 'am-add-time-frame-details-to-metrics-guide' into 'master'

Add time_frame to metrics guide

See merge request gitlab-org/gitlab!62660

doc/development/usage_ping/metrics_dictionary.md

@@ -71,6 +71,13 @@ In general, we avoid complex objects and prefer one of the `boolean`, `number`,
 An example of a metric that uses `value_type: object` is `topology` (`/config/metrics/settings/20210323120839_topology.yml`),
 which has a related schema in `/config/metrics/objects_schemas/topology_schema.json`.
 
+### Metric time_frame
+
+- `7d`: The metric data applies to the most recent 7-day interval. For example, the following metric counts the number of users that create epics over a 7-day interval: `ee/config/metrics/counts_7d/20210305145820_g_product_planning_epic_created_weekly.yml`.
+- `28d`: The metric data applies to the most recent 28-day interval. For example, the following metric counts the number of unique users that create issues over a 28-day interval: `config/metrics/counts_28d/20210216181139_issues.yml`.
+- `all`: The metric data applies for the whole time the metric has been active (all-time interval). For example, the following metric counts all users that create issues: `/config/metrics/counts_all/20210216181115_issues.yml`.
+- `none`: The metric collects a type of data that's not tracked over time, such as settings and configuration information. Therefore, a time interval is not applicable. For example, `uuid` has no time interval applicable: `config/metrics/license/20210201124933_uuid.yml`.
+
 ### Metric name
 
 To improve metric discoverability by a wider audience, each metric with