Add webhook rate-limit threshold for Free plan on gitlab.com

See https://gitlab.com/gitlab-org/gitlab/-/issues/330133

Changelog: changed

db/migrate/20210601131742_update_web_hook_calls_limit.rb

+# frozen_string_literal: true
+
+class UpdateWebHookCallsLimit < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  def up
+    return unless Gitlab.com?
+
+    create_or_update_plan_limit('web_hook_calls', 'free', 120)
+  end
+
+  def down
+    return unless Gitlab.com?
+
+    create_or_update_plan_limit('web_hook_calls', 'free', 0)
+  end
+end

db/schema_migrations/20210601131742

+63cd83e097a24b39a399918422950caacb6aed8d05d0d8b7bcf66f9155a0d04e
\ No newline at end of file

doc/administration/instance_limits.md

@@ -112,7 +112,7 @@ Limit the maximum daily member invitations allowed per group hierarchy.
 - GitLab.com: Free members may invite 20 members per day.
 - Self-managed: Invites are not limited.
 
-### Webhook calls
+### Webhook rate limit
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61151) in GitLab 13.12.
 > - [Deployed behind a feature flag](../user/feature_flags.md), disabled by default.

doc/user/gitlab_com/index.md

@@ -153,11 +153,13 @@ content directly from common public CDN hostnames.
 
 ## Webhooks
 
-A limit of:
+The following limits apply for [Webhooks](../project/integrations/webhooks.md):
 
-- 100 webhooks applies to projects.
-- 50 webhooks applies to groups. **(BRONZE ONLY)**
-- Payload is limited to 25MB.
+| Setting | GitLab.com | Default |
+| ------- | ---------- | ------- |
+| [Webhook rate limit](../../administration/instance_limits.md#webhook-rate-limit) | `120` calls per minute for Free tier, unlimited for all paid tiers | Unlimited
+| [Number of webhooks](../../administration/instance_limits.md#number-of-webhooks) | `100` per-project, `50` per-group | `100` per-project, `50` per-group
+| Maximum payload size | `25 MB` | `25 MB`
 
 ## Shared runners
 

doc/user/project/integrations/webhooks.md

@@ -34,8 +34,10 @@ Webhooks are available:
 - Per project, at a project's **Settings > Webhooks** menu. **(FREE)**
 - Additionally per group, at a group's **Settings > Webhooks** menu. **(PREMIUM)**
 
-NOTE:
-On GitLab.com, the [maximum number of webhooks and their size](../../../user/gitlab_com/index.md#webhooks) per project, and per group, is limited.
+GitLab.com enforces various [webhook limits](../../../user/gitlab_com/index.md#webhooks), including:
+
+- The maximum number of webhooks and their size, both per project, and per group.
+- The number of webhook calls per minute.
 
 ## Possible uses for webhooks