Documentation for the deprecated API endpoint rate limiter

Another substantial copy-paste!

doc/administration/instance_limits.md

@@ -102,6 +102,15 @@ This setting limits the request rate on the Packages API per user or IP address.
 
 - **Default rate limit**: Disabled by default.
 
+### Deprecated API endpoints
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68645) in GitLab 14.4.
+
+This setting limits the request rate on deprecated API endpoints per user or IP address. For more information, read
+[Deprecated API rate limits](../user/admin_area/settings/deprecated_api_rate_limits.md).
+
+- **Default rate limit**: Disabled by default.
+
 ### Import/Export
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/35728) in GitLab 13.2.

doc/security/rate_limits.md

@@ -36,6 +36,7 @@ These are rate limits you can set in the Admin Area of your instance:
 - [Package registry rate limits](../user/admin_area/settings/package_registry_rate_limits.md)
 - [Git LFS rate limits](../user/admin_area/settings/git_lfs_rate_limits.md)
 - [Files API rate limits](../user/admin_area/settings/files_api_rate_limits.md)
+- [Deprecated API rate limits](../user/admin_area/settings/deprecated_api_rate_limits.md)
 
 ## Non-configurable limits
 

doc/user/admin_area/settings/deprecated_api_rate_limits.md

+---
+stage: Create
+group: Source Code
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
+type: reference
+---
+
+# Deprecated API rate limits **(FREE SELF)**
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68645) in GitLab 14.4.
+
+Deprecated API endpoints are those which have been replaced with alternative
+functionality, but cannot be removed without breaking backward compatibility.
+Setting a restrictive rate limit on these endpoints can encourage users to
+switch to the alternatives.
+
+## Deprecated API endpoints
+
+Not all deprecated API endpoints are included in this rate limit - just those
+that might have a performance impact:
+
+- [`GET /groups/:id`](../../../api/groups.md#details-of-a-group) **without** the `with_projects=0` query parameter.
+
+## Define Deprecated API rate limits
+
+Rate limits for deprecated API endpoints are disabled by default. When enabled, they supersede
+the general user and IP rate limits for requests to deprecated endpoints. You can keep any general user
+and IP rate limits already in place, and increase or decrease the rate limits
+for deprecated API endpoints. No other new features are provided by this override.
+
+Prerequisites:
+
+- You must have the Administrator role for your instance.
+
+To override the general user and IP rate limits for requests to deprecated API endpoints:
+
+1. On the top bar, select **Menu > Admin**.
+1. On the left sidebar, select **Settings > Network**.
+1. Expand **Deprecated API Rate Limits**.
+1. Select the check boxes for the types of rate limits you want to enable:
+   - **Unauthenticated API request rate limit**
+   - **Authenticated API request rate limit**
+1. _If you enabled unauthenticated API request rate limits:_
+   1. Select the **Maximum unauthenticated API requests per period per IP**.
+   1. Select the **Unauthenticated API rate limit period in seconds**.
+1. _If you enabled authenticated API request rate limits:_
+   1. Select the **Maximum authenticated API requests per period per user**.
+   1. Select the **Authenticated API rate limit period in seconds**.
+
+## Resources
+
+- [Rate limits](../../../security/rate_limits.md)
+- [User and IP rate limits](user_and_ip_rate_limits.md)

doc/user/admin_area/settings/index.md

@@ -99,6 +99,7 @@ To access the default page for Admin Area settings:
 | [Package Registry Rate Limits](package_registry_rate_limits.md) | Configure specific limits for Packages API requests that supersede the user and IP rate limits. |
 | [Git LFS Rate Limits](git_lfs_rate_limits.md) | Configure specific limits for Git LFS requests that supersede the user and IP rate limits. |
 | [Files API Rate Limits](files_api_rate_limits.md) | Configure specific limits for Files API requests that supersede the user and IP rate limits. |
+| [Deprecated API Rate Limits](deprecated_api_rate_limits.md) | Configure specific limits for deprecated API requests that supersede the user and IP rate limits. |
 | [Outbound requests](../../../security/webhooks.md) | Allow requests to the local network from hooks and services. |
 | [Protected Paths](protected_paths.md) | Configure paths to be protected by Rack Attack. |
 | [Incident Management](../../../operations/incident_management/index.md) Limits | Limit the number of inbound alerts that can be sent to a project. |

doc/user/admin_area/settings/user_and_ip_rate_limits.md

@@ -191,6 +191,8 @@ The possible names are:
 - `throttle_authenticated_git_lfs`
 - `throttle_unauthenticated_files_api`
 - `throttle_authenticated_files_api`
+- `throttle_unauthenticated_deprecated_api`
+- `throttle_authenticated_deprecated_api`
 
 For example, to try out throttles for all authenticated requests to
 non-protected paths can be done by setting