Add docs about naming project bot users, and not using seat

doc/subscriptions/index.md

@@ -76,7 +76,7 @@ Every occupied seat, whether by person, job, or bot is counted in the subscripti
 renewal of a subscription won't be counted as active users for the renewal subscription. They may
 count as active users in the subscription period in which they were originally added.
 - Members with Guest permissions on an Ultimate subscription.
-- GitLab-created service accounts: `Ghost User` and `Support Bot`.
+- GitLab-created service accounts: `Ghost User`, `Support Bot` and [`Project bot users`](../user/project/settings/project_access_tokens.md#project-bot-users).
 
 ##### Users statistics
 

doc/user/project/settings/project_access_tokens.md

@@ -38,8 +38,14 @@ For examples of how you can use a project access token to authenticate with the
 ## Project bot users
 
 For each project access token created, a bot user will also be created and added to the project with
-["Maintainer" level permissions](../../permissions.md#project-members-permissions). API calls made with a
-project access token will be associated to the corresponding bot user.
+["Maintainer" level permissions](../../permissions.md#project-members-permissions).
+
+For the bot:
+
+- The name is set to the name of the token.
+- The username is set to `project_{project_id}_bot`, such as `project_123_bot`.
+
+API calls made with a project access token are associated with the corresponding bot user.
 
 These users will appear in **Members** but can not be modified.
 Furthermore, the bot user can not be added to any other project.
@@ -48,6 +54,8 @@ When the project access token is [revoked](#revoking-a-project-access-token) the
 records will be moved to a system-wide user with the username "Ghost User". For more information,
 see [Associated Records](../../profile/account/delete_account.md#associated-records).
 
+Project bot users are a [GitLab-created service account](../../../subscriptions/index.md#self-managed) and do not count as a licensed seat.
+
 ## Revoking a project access token
 
 At any time, you can revoke any project access token by clicking the