Use iso8601 timestamps in annotation grapql

To assure firefox compatibility we should use iso stadard fromat

app/graphql/types/metrics/dashboards/annotation_type.rb

@@ -16,10 +16,10 @@ module Types
         field :panel_id, GraphQL::STRING_TYPE, null: true,
               description: 'ID of a dashboard panel to which the annotation should be scoped'
 
-        field :starting_at, GraphQL::STRING_TYPE, null: true,
+        field :starting_at, Types::TimeType, null: true,
               description: 'Timestamp marking start of annotated time span'
 
-        field :ending_at, GraphQL::STRING_TYPE, null: true,
+        field :ending_at, Types::TimeType, null: true,
               description: 'Timestamp marking end of annotated time span'
 
         def panel_id

changelogs/unreleased/mwaw-216963-annotations-missing-from-metric-charts.yml

+---
+title: Use iso 8601 timestamp format in metrics dashboard annotations graphql resource
+  to assure multi browser compatibility
+merge_request: 31474
+author:
+type: fixed

doc/api/graphql/reference/gitlab_schema.graphql

@@ -6031,7 +6031,7 @@ type MetricsDashboardAnnotation {
   """
   Timestamp marking end of annotated time span
   """
-  endingAt: String
+  endingAt: Time
 
   """
   ID of the annotation
@@ -6046,7 +6046,7 @@ type MetricsDashboardAnnotation {
   """
   Timestamp marking start of annotated time span
   """
-  startingAt: String
+  startingAt: Time
 }
 
 """

doc/api/graphql/reference/gitlab_schema.json

@@ -16936,7 +16936,7 @@
               ],
               "type": {
                 "kind": "SCALAR",
-                "name": "String",
+                "name": "Time",
                 "ofType": null
               },
               "isDeprecated": false,
@@ -16982,7 +16982,7 @@
               ],
               "type": {
                 "kind": "SCALAR",
-                "name": "String",
+                "name": "Time",
                 "ofType": null
               },
               "isDeprecated": false,

doc/api/graphql/reference/index.md

@@ -915,10 +915,10 @@ Autogenerated return type of MergeRequestSetWip
 | Name  | Type  | Description |
 | ---   |  ---- | ----------  |
 | `description` | String | Description of the annotation |
-| `endingAt` | String | Timestamp marking end of annotated time span |
+| `endingAt` | Time | Timestamp marking end of annotated time span |
 | `id` | ID! | ID of the annotation |
 | `panelId` | String | ID of a dashboard panel to which the annotation should be scoped |
-| `startingAt` | String | Timestamp marking start of annotated time span |
+| `startingAt` | Time | Timestamp marking start of annotated time span |
 
 ## Milestone
 

spec/requests/api/graphql/metrics/dashboard/annotations_spec.rb

@@ -82,7 +82,7 @@ describe 'Getting Metrics Dashboard Annotations' do
                                               "description" => annotation.description,
                                               "id" => annotation.to_global_id.to_s,
                                               "panelId" => annotation.panel_xid,
-                                              "startingAt" => annotation.starting_at.to_s,
+                                              "startingAt" => annotation.starting_at.iso8601,
                                               "endingAt" => nil
                                             }]
       end