Add feature flag to incident escalation docs

It was expected that this feature would be enabled earlier, but that 
didn't ultimately happen. This updates the documentation to reflect the 
current state and expected functionality.

doc/operations/incident_management/incidents.md

@@ -255,7 +255,12 @@ Add a to-do for incidents that you want to track in your to-do list. Click the
 
 ### Change incident status
 
-> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/5716) in GitLab 14.9.
+> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/5716) in GitLab 14.9 [with a flag](../../administration/feature_flags.md) named `incident_escalations`. Disabled by default.
+
+FLAG:
+By default this feature is not available. To make it available per project or for your entire
+instance, ask an administrator to [enable the feature flag](../../administration/feature_flags.md)
+named `incident_escalations`.
 
 For users with the Developer role or higher, select **Edit** in the **Status** section of the
 right-hand side bar of an incident, then select a status. **Triggered** is the default status for
@@ -273,7 +278,12 @@ updating the incident status also updates the alert status.
 
 ## Change escalation policy **(PREMIUM)**
 
-> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/5716) in GitLab 14.9.
+> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/5716) in GitLab 14.9 [with a flag](../../administration/feature_flags.md) named `incident_escalations`. Disabled by default.
+
+FLAG:
+By default this feature is not available. To make it available per project or for your entire
+instance, ask an administrator to [enable the feature flag](../../administration/feature_flags.md)
+named `incident_escalations`.
 
 For users with the Developer role or higher, select **Edit** in the **Escalation policy** section of
 the right-hand side bar of an incident, then select a policy. By default, new incidents do not have

doc/operations/incident_management/paging.md

@@ -50,7 +50,12 @@ or stop alert escalations by [updating the alert's status](alerts.md#update-an-a
 
 ### Escalating an incident
 
-> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/5716) in GitLab 14.9.
+> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/5716) in GitLab 14.9 [with a flag](../../administration/feature_flags.md) named `incident_escalations`. Disabled by default.
+
+FLAG:
+By default this feature is not available. To make it available per project or for your entire
+instance, ask an administrator to [enable the feature flag](../../administration/feature_flags.md)
+named `incident_escalations`.
 
 For incidents, paging on-call responders is optional for each individual incident.
 To begin escalating the incident, [set the incident's escalation policy](incidents.md#change-escalation-policy).

doc/user/project/integrations/webhook_events.md

@@ -203,7 +203,7 @@ The `assignee` and `assignee_id` keys are deprecated
 and contain the first assignee only.
 
 The `escalation_status` and `escalation_policy` fields are
-only available for issue types which support escalations,
+only available for issue types which [support escalations](../../../operations/incident_management/paging.md#paging),
 such as incidents.
 
 Request header: