Make milestone required in metric definition

config/metrics/schema.json

 {
   "type": "object",
-  "required": ["key_path", "description", "value_type", "status", "product_group", "time_frame", "data_source", "distribution", "tier", "data_category"],
+  "required": ["key_path", "description", "value_type", "status", "product_group", "time_frame", "data_source", "distribution", "tier", "data_category", "milestone"],
   "properties": {
     "key_path": {
       "type": "string"
@@ -33,7 +33,7 @@
       "enum": ["active", "data_available", "implemented", "deprecated", "removed", "broken"]
     },
     "milestone": {
-      "type": ["string", "null"],
+      "type": ["string"],
       "pattern": "^<?[0-9]+\\.[0-9]+$"
     },
     "milestone_removed": {

ee/config/metrics/counts_28d/20210618101233_cluster_image_scanning_scans.yml

@@ -7,6 +7,8 @@ product_group: group::container security
 product_category: container_scanning
 value_type: number
 status: implemented
+milestone: "14.1"
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64877
 time_frame: 28d
 data_source: database
 data_category: optional

ee/config/metrics/counts_28d/20210618125224_cluster_image_scanning_pipeline.yml

@@ -7,6 +7,8 @@ product_group: group::container security
 product_category: container_scanning
 value_type: number
 status: implemented
+milestone: "14.1"
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64877
 time_frame: 28d
 data_source: database
 data_category: optional

ee/config/metrics/counts_28d/20210830231329_sast_scans.yml

@@ -7,6 +7,7 @@ product_group: group::static analysis
 product_category: static_application_security_testing
 value_type: number
 status: data_available
+milestone: "<13.9"
 time_frame: 28d
 data_source: database
 data_category: operational

ee/config/metrics/counts_28d/20210830231849_container_scanning_scans.yml

@@ -7,6 +7,7 @@ product_group: group::container security
 product_category: container_scanning
 value_type: number
 status: data_available
+milestone: "13.9"
 time_frame: 28d
 data_source: database
 data_category: operational

ee/config/metrics/counts_28d/20210830231956_secret_detection_scans.yml

@@ -7,6 +7,7 @@ product_group: group::static analysis
 product_category: secret_detection
 value_type: number
 status: data_available
+milestone: "<13.9"
 time_frame: 28d
 data_source: database
 data_category: operational

ee/config/metrics/counts_all/20210618124854_cluster_image_scanning_scans.yml

@@ -7,6 +7,8 @@ product_group: group::container security
 product_category: container_scanning
 value_type: number
 status: implemented
+milestone: "14.1"
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64877
 time_frame: all
 data_source: database
 data_category: optional

spec/lib/gitlab/usage/metric_definition_spec.rb

@@ -10,6 +10,7 @@ RSpec.describe Gitlab::Usage::MetricDefinition do
       product_category: 'collection',
       product_stage: 'growth',
       status: 'active',
+      milestone: '14.1',
       default_generation: 'generation_1',
       key_path: 'uuid',
       product_group: 'group::product analytics',
@@ -64,6 +65,7 @@ RSpec.describe Gitlab::Usage::MetricDefinition do
       :value_type         | nil
       :value_type         | 'test'
       :status             | nil
+      :milestone          | nil
       :data_category      | nil
       :key_path           | nil
       :product_group      | nil
@@ -190,6 +192,7 @@ RSpec.describe Gitlab::Usage::MetricDefinition do
         product_category: 'collection',
         product_stage: 'growth',
         status: 'active',
+        milestone: '14.1',
         default_generation: 'generation_1',
         key_path: 'counter.category.event',
         product_group: 'group::product analytics',