[DOCS][Cases][9.3 & Serverless]: Update IBM Resilient case connector docs (#4179)

## Summary
Fixes #3977. Under the
step for adding a connector to a new case, I've added an important
detail about the IBM resilient connector. Also updated the name of the
section that the step was referring to. At some point, the section name
was changed from **External incident management system** to **External
Connector Fields**.

## Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this
contribution?
- [ ] Yes  
- [x] No  


## Preview

#4179 (comment)

Author: nastasha-solomon

explore-analyze/alerts-cases/cases/manage-cases.md

@@ -31,8 +31,14 @@ Open a new case to keep track of issues and share their details with colleagues.
 
 4. Optionally, add a category, assignees, and tags. You can add users only if they meet the necessary [prerequisites](setup-cases.md).
 5. If you defined any [custom fields](manage-cases-settings.md#case-custom-fields), they appear in the **Additional fields** section.
+6. (Optional) Under **External Connector Fields**, you can select a connector to send cases to an external system. If you’ve created any connectors previously, they will be listed here. If there are no connectors listed, you can create one. For more information, refer to [External incident management systems](manage-cases-settings.md#case-connectors).
+
+    ::::{note}
+    :applies_to:{stack: ga 9.3}
+    When specifying **Additional fields** for an {{ibm-r}} connector, fields that are set when an incident is created or changed (for example, an incident is closed) won't display as an option.
+    ::::
+
 
-6. For the **External incident management system**, select a connector. For more information, refer to [External incident management systems](manage-cases-settings.md#case-connectors).
 7. After you’ve completed all of the required fields, click **Create case**.
 
 {applies_to}`stack: preview` {applies_to}`serverless: preview` Alternatively, you can configure your rules to automatically create cases by using [case actions](kibana://reference/connectors-kibana/cases-action-type.md). By default, the rule adds all of the alerts within a specified time window to a single case. You can optionally choose a field to group the alerts and create separate cases for each group. You can also choose whether you want the rule to reopen cases or open new ones when the time window elapses.

solutions/observability/incident-management/create-manage-cases.md

@@ -35,7 +35,13 @@ Open a new case to keep track of issues and share the details with colleagues. T
     **For Elastic Stack**, You can add users only if they meet the necessary [prerequisites](/solutions/observability/incident-management/configure-access-to-cases.md).
 
 6. If you defined [custom fields](/solutions/observability/incident-management/configure-case-settings.md#case-custom-fields), they appear in the **Additional fields** section.
-7. (Optional) Under External incident management system, you can select a connector to send cases to an external system. If you’ve created any connectors previously, they will be listed here. If there are no connectors listed, you can [create one](/solutions/observability/incident-management/configure-case-settings.md).
+7. (Optional) Under **External Connector Fields**, you can select a connector to send cases to an external system. If you’ve created any connectors previously, they will be listed here. If there are no connectors listed, you can create one. For more information, refer to [External incident management systems](/solutions/observability/incident-management/configure-case-settings.md#cases-external-connectors).
+
+    ::::{note}
+    :applies_to:{stack: ga 9.3}
+    When specifying **Additional fields** for an {{ibm-r}} connector, fields that are set when an incident is created or changed (for example, an incident is closed) won't display as an option.
+    ::::
+
 8. After you’ve completed all of the required fields, click **Create case**.
 
 ::::{tip}
@@ -76,7 +82,7 @@ There is a 10 MiB size limit for images. For all other MIME types, the limit is
 
 ## Send cases to external incident management systems [observability-create-a-new-case-send-cases-to-external-incident-management-systems]
 
-To send a case to an external system, click the ![push](/solutions/images/serverless-importAction.svg "") button in the *External incident management system* section of the individual case page. This information is not sent automatically. If you make further changes to the shared case fields, you should push the case again.
+To send a case to an external system, click the ![push](/solutions/images/serverless-importAction.svg "") button in the **External incident management system** section of the individual case page. This information is not sent automatically. If you make further changes to the shared case fields, you should push the case again.
 
 For more information about configuring connections to external incident management systems, refer to [](/solutions/observability/incident-management/configure-case-settings.md).
 

solutions/security/investigate/open-manage-cases.md

@@ -38,7 +38,13 @@ Open a new case to keep track of security issues and share their details with co
 5. {applies_to}`stack: preview` {applies_to}`serverless: preview` If you defined [custom fields](/solutions/security/investigate/configure-case-settings.md#cases-ui-custom-fields), they appear in the **Additional fields** section.
 6. Choose if you want alert statuses to sync with the case’s status after they are added to the case. This option is turned on by default, but you can turn it off after creating the case.
 7. {applies_to}`stack: ga 9.2` With the appropriate [{{stack}} subscription](https://www.elastic.co/pricing) or [{{serverless-short}} project feature tier](../../../deploy-manage/deploy/elastic-cloud/project-settings.md), you can choose to automatically extract observables from alerts that you're adding to the case. This option is turned on by default. You can turn it off after creating the case by toggling **Auto-extract observables** on the case's **Observables** tab.
-8. From **External incident management**, select a [connector](/solutions/security/investigate/configure-case-settings.md#cases-ui-integrations). If you’ve previously added one, that connector displays as the default selection. Otherwise, the default setting is `No connector selected`.
+8. (Optional) Under **External Connector Fields**, you can select a connector to send cases to an external system. If you’ve created any connectors previously, they will be listed here. If there are no connectors listed, you can create one. For more information, refer to [External incident management systems](/solutions/security/investigate/configure-case-settings.md#cases-ui-integrations)
+
+    ::::{note}
+    :applies_to:{stack: ga 9.3}
+    When specifying **Additional fields** for an {{ibm-r}} connector, fields that are set when an incident is created or changed (for example, an incident is closed) won't display as an option.
+    ::::
+
 9. Click **Create case**.
 
     ::::{note}