Add 13.8.3 as an intermediate stop for upgrade paths

doc/update/index.md

@@ -182,7 +182,7 @@ Find where your version sits in the upgrade path below, and upgrade GitLab
 accordingly, while also consulting the
 [version-specific upgrade instructions](#version-specific-upgrading-instructions):
 
-`8.11.Z` -> [`8.12.0`](#upgrades-from-versions-earlier-than-812) -> `8.17.7` -> `9.5.10` -> `10.8.7` -> [`11.11.8`](#1200) -> `12.0.12` -> [`12.1.17`](#1210) -> `12.10.14` -> `13.0.14` -> [`13.1.11`](#1310) -> [latest `13.12.Z`](https://about.gitlab.com/releases/categories/releases/) -> [latest `14.0.Z`](#1400) -> [`14.1.Z`](#1410) -> [latest `14.Y.Z`](https://about.gitlab.com/releases/categories/releases/)
+`8.11.Z` -> [`8.12.0`](#upgrades-from-versions-earlier-than-812) -> `8.17.7` -> `9.5.10` -> `10.8.7` -> [`11.11.8`](#1200) -> `12.0.12` -> [`12.1.17`](#1210) -> `12.10.14` -> `13.0.14` -> [`13.1.11`](#1310) -> [`13.8.3`](#1383) -> [latest `13.12.Z`](https://about.gitlab.com/releases/categories/releases/) -> [latest `14.0.Z`](#1400) -> [`14.1.Z`](#1410) -> [latest `14.Y.Z`](https://about.gitlab.com/releases/categories/releases/)
 
 The following table, while not exhaustive, shows some examples of the supported
 upgrade paths.
@@ -190,7 +190,7 @@ upgrade paths.
 | Target version | Your version | Supported upgrade path                                                                               | Note                                                                                                                              |
 | -------------- | ------------ | ---------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------- |
 | `14.1.2`       | `13.9.2`     | `13.9.2` -> `13.12.9` -> `14.0.7` -> `14.1.2`                                                        | Two intermediate versions are required: `13.12` and `14.0`, then `14.1`.                                                          |
-| `13.5.4`       | `12.9.2`     | `12.9.2` -> `12.10.14` -> `13.0.14`  -> `13.1.11` -> `13.5.4`                                        | Three intermediate versions are required: `12.10`, `13.0` and `13.1`, then `13.5.4`.                                              |
+| `13.12.10`     | `12.9.2`     | `12.9.2` -> `12.10.14` -> `13.0.14`  -> `13.1.11` -> `13.8.3` -> `13.12.10`                          | Four intermediate versions are required: `12.10`, `13.0`, `13.1` and `13.8.3`, then `13.12.10`.                               |
 | `13.2.10`      | `11.5.0`     | `11.5.0` -> `11.11.8` -> `12.0.12` -> `12.1.17` -> `12.10.14` -> `13.0.14` -> `13.1.11` -> `13.2.10` | Six intermediate versions are required: `11.11`, `12.0`, `12.1`, `12.10`, `13.0` and `13.1`, then `13.2.10`.                      |
 | `12.10.14`     | `11.3.4`     | `11.3.4` -> `11.11.8` -> `12.0.12` -> `12.1.17` -> `12.10.14`                                        | Three intermediate versions are required: `11.11`, `12.0` and `12.1`, then `12.10.14`.                                            |
 | `12.9.5`       | `10.4.5`     | `10.4.5` -> `10.8.7` -> `11.11.8` -> `12.0.12` -> `12.1.17` -> `12.9.5`                              | Four intermediate versions are required: `10.8`, `11.11`, `12.0` and `12.1`, then `12.9.5`.                                       |
@@ -480,6 +480,17 @@ DETAIL: trigger trigger_0d588df444c8 on table application_settings depends on co
 To work around this bug, follow the previous steps to complete the update.
 More details are available [in this issue](https://gitlab.com/gitlab-org/gitlab/-/issues/324160).
 
+### 13.8.3
+
+GitLab 13.8 includes a background migration to address [an issue with duplicate service records](https://gitlab.com/gitlab-org/gitlab/-/issues/290008). If duplicate services are present, this background migration must complete before a unique index is applied to the services table, which was [introduced in GitLab 13.9](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/52563). Upgrades from GitLab 13.8 and earlier to later versions must include an intermediate upgrade to GitLab 13.8.3 and [must wait until the background migrations complete](#checking-for-background-migrations-before-upgrading) before proceeding.
+
+If duplicate services are still present, an upgrade to 13.9.x or later results in a failed upgrade with the following error:
+
+```console
+PG::UniqueViolation: ERROR:  could not create unique index "index_services_on_project_id_and_type_unique"
+DETAIL:  Key (project_id, type)=(NNN, ServiceName) is duplicated.
+```
+
 ### 13.6.0
 
 Ruby 2.7.2 is required. GitLab does not start with Ruby 2.6.6 or older versions.