Documentation for On-Demand Release Evidence

Part of https://gitlab.com/gitlab-org/gitlab/issues/199065

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/26760

doc/api/releases/index.md

@@ -456,6 +456,33 @@ Example response:
 }
 ```
 
+## Collect release evidence **(PREMIUM ONLY)**
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/199065) in [GitLab Premium](https://about.gitlab.com/pricing/) 12.10.
+
+Create Evidence for an existing Release.
+
+```plaintext
+POST /projects/:id/releases/:tag_name/evidence
+```
+
+| Attribute     | Type           | Required | Description                                                                         |
+| ------------- | -------------- | -------- | ----------------------------------------------------------------------------------- |
+| `id`          | integer/string | yes      | The ID or [URL-encoded path of the project](../README.md#namespaced-path-encoding). |
+| `tag_name`    | string         | yes      | The tag where the release will be created from.                                     |
+
+Example request:
+
+```shell
+curl --request POST --header "PRIVATE-TOKEN: gDybLx3yrUK_HLp3qPjS" "https://gitlab.example.com/api/v4/projects/24/releases/v0.1/evidence"
+```
+
+Example response:
+
+```json
+200
+```
+
 ## Update a release
 
 Update a Release.

doc/user/project/releases/index.md

@@ -244,16 +244,20 @@ You can also edit an existing tag to add release notes:
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/26019) in GitLab 12.6.
 
-Each time a new release is created, specific related data is collected in
-parallel. This dataset will be a snapshot this new release (including linked
-milestones and issues) at moment of creation. Such collection of data will
-provide a chain of custody and facilitate processes like external audits, for example.
+Each time a release is created, GitLab takes a snapshot of data that's related to it.
+This data is called Release Evidence. It includes linked milestones and issues, and
+it is taken at moment the release is created. It provides a chain of custody and can
+facilitate processes like external audits, for example.
 
-The gathered evidence data is stored in the database upon creation of a new
-release as a JSON object. In GitLab 12.6, a link to
-the evidence data is provided for [each Release](#releases-list).
+You can also [use the API](../../../api/releases/index.md#collect-release-evidence-premium-only) to
+generate Release Evidence for an existing release. Because of this, [each release](#releases-list)
+can have multiple Release Evidence snapshots. You can view the Release Evidence and
+its details on the Release page.
 
-Here is what this object can look like:
+Release Evidence is stored as a JSON object, so you can compare evidence by using
+commonly-available tools.
+
+Here is an example of a Release Evidence object:
 
 ```json
 {
@@ -319,7 +323,14 @@ Please note that Release Evidence's data is collected regardless of this
 feature flag, which only enables or disables the display of the data on the
 Releases page.
 
-### Scheduled Evidence creation
+### Collect release evidence **(PREMIUM ONLY)**
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/199065) in [GitLab Premium](https://about.gitlab.com/pricing/) 12.10.
+
+Evidence collection can be initiated by using an [API call](../../../api/releases/index.md#collect-release-evidence-premium-only) at any time. Evidence snapshots are visible on
+the Release page, along with the timestamp the Evidence was collected.
+
+### Schedule release evidence collection
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/23697) in GitLab 12.8.