Announce deprecation for iteration started field

data/deprecations/14-8-iteration-started-field.yml

+- name: "`started` iterations API field" # The name of the feature to be deprecated
+  announcement_milestone: "14.8" # The milestone when this feature was first announced as deprecated.
+  announcement_date: "2022-02-22" # The date of the milestone release when this feature was first announced as deprecated. This should almost always be the 22nd of a month (YYYY-MM-22), unless you did an out of band blog post.
+  removal_milestone: "15.0" # The milestone when this feature is planned to be removed
+  removal_date: "2022-05-22" # The date of the milestone release when this feature was first announced as deprecated. This should almost always be the 22nd of a month (YYYY-MM-22), unless you did an out of band blog post.
+  breaking_change: true # If this deprecation is a breaking change, set this value to true
+  body: | # Do not modify this line, instead modify the lines below.
+    The `started` field in the [iterations API](https://docs.gitlab.com/ee/api/iterations.html#list-project-iterations) is being deprecated and will be removed in GitLab 15.0. This field is being replaced with the `current` field (already available) which aligns with the naming for other time-based entities, such as milestones.
+# The following items are not published on the docs page, but may be used in the future.
+  stage: plan
+  tiers: # (optional - may be required in the future) An array of tiers that the feature is available in currently.  e.g., [Free, Silver, Gold, Core, Premium, Ultimate]
+  issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/334018
+  documentation_url: # (optional) This is a link to the current documentation page
+  image_url: # (optional) This is a link to a thumbnail image depicting the feature
+  video_url: # (optional) Use the youtube thumbnail URL with the structure of https://img.youtube.com/vi/UNIQUEID/hqdefault.jpg

doc/update/deprecations.md

@@ -716,3 +716,15 @@ Support for `fixup!` is now considered deprecated, and will be
 removed in GitLab 15.0.
 
 **Planned removal milestone: 15.0 (2022-06-22)**
+
+### `started` iterations API field
+
+WARNING:
+This feature will be changed or removed in 15.0
+as a [breaking change](https://docs.gitlab.com/ee/development/contributing/#breaking-changes).
+Before updating GitLab, review the details carefully to determine if you need to make any
+changes to your code, settings, or workflow.
+
+The `started` field in the [iterations API](https://docs.gitlab.com/ee/api/iterations.html#list-project-iterations) is being deprecated and will be removed in GitLab 15.0. This field is being replaced with the `current` field (already available) which aligns with the naming for other time-based entities, such as milestones.
+
+**Planned removal milestone: 15.0 (2022-05-22)**