Add sharding keys for continuous_integration

Add sharding keys for feature category `continuous_integration`.

These tables have been identified as
[cell local tables](https://docs.gitlab.com/ee/development/database/multiple_databases.html#guidelines-on-choosing-between-gitlab_main_cell-and-gitlab_main_clusterwide-schema).

All cell local tables require a
[sharding key](https://docs.gitlab.com/ee/development/database/multiple_databases.html#defining-a-sharding-key-for-all-cell-local-tables).

A sharding key has been automatically selected for these tables. The sharding key was chosen because it is a
`NOT NULL` column referencing either `projects` or `namespaces`.

Additionally, `gitlab_schema` has been set to `gitlab_main_cell` for any tables didn't use this schema already.
For these tables we have also added `allow_cross_joins`, `allow_cross_transactions` and
`allow_cross_foreign_keys`. These will silence any existing violations, allowing the pipeline to pass without
requiring further changes. In the future, we'll remove these `allow_...` statements and fix any violations as
they arise. You can read more about this in the [documentation for multiple databases](https://docs.gitlab.com/ee/development/database/multiple_databases.html)

We have assigned a random backend engineer from ~"group::pipeline execution" to review these changes.
Please confirm that each table should indeed be cell local, and that the selected column is an appropriate
sharding key. When you are finished, please request a review from the database maintainer suggested by Danger.

If you have any questions or concerns, reach out to @tigerwnz or @DylanGriffith.

This change was generated by
[gitlab-housekeeper](https://gitlab.com/gitlab-org/gitlab/-/tree/master/gems/gitlab-housekeeper)

Changelog: other

db/docs/ci_job_token_project_scope_links.yml

@@ -4,10 +4,12 @@ classes:
 - Ci::JobToken::ProjectScopeLink
 feature_categories:
 - continuous_integration
-description: |
-  Links a source project and target project, allowing a project's job token to give access to another project.
-  Using the outbound direction, the source project's job token can access target projects.
-  Using the inbound direction, the source project can be accessed by the target project's job token.
+description: Links a source project and target project, allowing a project's job token
+  to give access to another project. Using the outbound direction, the source project's
+  job token can access target projects. Using the inbound direction, the source project
+  can be accessed by the target project's job token.
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/62733
 milestone: '14.0'
 gitlab_schema: gitlab_ci
+sharding_key:
+  source_project_id: projects

db/docs/ci_namespace_monthly_usages.yml

@@ -8,3 +8,5 @@ description: TODO
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/52915
 milestone: '13.9'
 gitlab_schema: gitlab_ci
+sharding_key:
+  namespace_id: namespaces

db/docs/ci_pending_builds.yml

@@ -8,3 +8,5 @@ description: Pending builds metadata
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61581
 milestone: '14.0'
 gitlab_schema: gitlab_ci
+sharding_key:
+  project_id: projects

db/docs/ci_pipeline_metadata.yml

@@ -8,3 +8,5 @@ description: Stores additional information about CI pipelines
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/97139
 milestone: '15.5'
 gitlab_schema: gitlab_ci
+sharding_key:
+  project_id: projects

db/docs/ci_project_monthly_usages.yml

@@ -8,3 +8,5 @@ description: TODO
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/53460
 milestone: '13.9'
 gitlab_schema: gitlab_ci
+sharding_key:
+  project_id: projects

db/docs/ci_refs.yml

@@ -8,3 +8,5 @@ description: TODO
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/16951
 milestone: '12.9'
 gitlab_schema: gitlab_ci
+sharding_key:
+  project_id: projects

db/docs/ci_running_builds.yml

@@ -4,13 +4,14 @@ classes:
 - Ci::RunningBuild
 feature_categories:
 - continuous_integration
-description: >
-  Running builds metadata.
-  Despite the generic `RunningBuild` name, in this first iteration it applies only to shared runners.
-  The decision to insert all of the running builds here was deferred to avoid the pressure on the database as
-  at this time that was not necessary.
-  We can reconsider the decision to limit this only to shared runners when there is more evidence that inserting all
-  of the running builds there is worth the additional pressure.
+description: Running builds metadata. Despite the generic `RunningBuild` name, in
+  this first iteration it applies only to shared runners. The decision to insert all
+  of the running builds here was deferred to avoid the pressure on the database as
+  at this time that was not necessary. We can reconsider the decision to limit this
+  only to shared runners when there is more evidence that inserting all of the running
+  builds there is worth the additional pressure.
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/62912
 milestone: '14.0'
 gitlab_schema: gitlab_ci
+sharding_key:
+  project_id: projects

db/docs/ci_sources_projects.yml

@@ -8,3 +8,5 @@ description: TODO
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/20063
 milestone: '12.9'
 gitlab_schema: gitlab_ci
+sharding_key:
+  source_project_id: projects

db/docs/ci_subscriptions_projects.yml

@@ -8,3 +8,5 @@ description: TODO
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/18678
 milestone: '12.5'
 gitlab_schema: gitlab_ci
+sharding_key:
+  downstream_project_id: projects

db/docs/external_pull_requests.yml

@@ -8,3 +8,5 @@ description: TODO
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/commit/ca6a1f33f91a8cceadebfb9c4e9ac6afa340f71d
 milestone: '12.3'
 gitlab_schema: gitlab_ci
+sharding_key:
+  project_id: projects

db/docs/merge_trains.yml

@@ -4,7 +4,16 @@ classes:
 - MergeTrains::Car
 feature_categories:
 - continuous_integration
-description: Each record represents a single merge request which is or was part of a merge train.
+description: Each record represents a single merge request which is or was part of
+  a merge train.
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/commit/827fc3ccb9335aa29fba0fc532b70015ec4c5186
 milestone: '11.11'
-gitlab_schema: gitlab_main
+gitlab_schema: gitlab_main_cell
+allow_cross_joins:
+- gitlab_main_clusterwide
+allow_cross_transactions:
+- gitlab_main_clusterwide
+allow_cross_foreign_keys:
+- gitlab_main_clusterwide
+sharding_key:
+  target_project_id: projects

db/docs/namespace_ci_cd_settings.yml

@@ -8,4 +8,12 @@ feature_categories:
 description: Namespace-scoped settings related to the CI/CD domain
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/86477
 milestone: '15.0'
-gitlab_schema: gitlab_main
+gitlab_schema: gitlab_main_cell
+allow_cross_joins:
+- gitlab_main_clusterwide
+allow_cross_transactions:
+- gitlab_main_clusterwide
+allow_cross_foreign_keys:
+- gitlab_main_clusterwide
+sharding_key:
+  namespace_id: namespaces

db/docs/p_ci_builds_metadata.yml

@@ -8,3 +8,5 @@ description: Routing table that holds information for job execution
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/100115
 milestone: '15.5'
 gitlab_schema: gitlab_ci
+sharding_key:
+  project_id: projects

db/docs/project_ci_cd_settings.yml

@@ -10,3 +10,5 @@ description: Project-scoped settings related to the CI/CD domain
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/commit/392c411bdc16386ef42c86afaf8c4d8e4cddb955
 milestone: '10.8'
 gitlab_schema: gitlab_main_cell
+sharding_key:
+  project_id: projects