Add GCP Cloud Monitoring webhook integration documentation

Add documentation for setting up a webhook notification channel in GCP Cloud
Monitoring to forward alerts to Robusta. This covers creating a managed webhook
channel with basic authentication using the Robusta account ID and API key.

Author: claude

docs/configuration/alertmanager-integration/gcp-monitoring.rst

@@ -0,0 +1,54 @@
+GCP Cloud Monitoring Integration with Robusta
+=============================================
+
+.. note::
+    This feature is available with the Robusta SaaS platform and self-hosted commercial plans. It is not available in the open-source version.
+
+This guide explains how to forward **GCP Cloud Monitoring alerts** to Robusta via a managed notification channel webhook.
+
+Requirements
+------------
+
+- Robusta is deployed and running.
+- You have access to the Robusta UI (to create an API key and find your ``account_id``).
+- You have access to GCP Cloud Monitoring with permissions to create notification channels.
+
+Step 1: Get Robusta Account ID and API Key
+------------------------------------------
+
+1. In the Robusta UI, go to **Settings -> API Keys**.
+2. Click **New API Key**, select **Alerts: Write** permissions, and **Save**.
+3. Copy the generated API key — you will use it as the password for basic authentication.
+4. Find your ``account_id``:
+
+   - In Robusta, the ``account_id`` appears in your **generated_values.yaml** file (from installation), or
+   - In the Robusta UI under **Settings -> Workspace**.
+
+Step 2: Create a Webhook Notification Channel in GCP
+----------------------------------------------------
+
+1. In the GCP Console, navigate to **Monitoring -> Alerting -> Edit Notification Channels**.
+2. Under **Webhooks**, click **Add New**.
+3. Configure the webhook with the following settings:
+
+   - **Display Name**: ``RobustaWebhook``
+   - **Endpoint URL**: ``https://api.robusta.dev/integrations/generic/gcp``
+   - **Authentication**: Select **Basic Authentication**
+   - **Username**: Your Robusta ``account_id`` from Step 1
+   - **Password**: Your Robusta API key from Step 1
+
+4. Click **Save** to create the notification channel.
+
+Step 3: Use the Webhook in Alerting Policies
+--------------------------------------------
+
+1. Navigate to **Monitoring -> Alerting -> Policies**.
+2. Create a new alerting policy or edit an existing one.
+3. In the **Notifications** section, select the **RobustaWebhook** notification channel.
+4. Save the alerting policy.
+
+Validation
+----------
+
+- Trigger a test alert or wait for an existing alerting policy to fire.
+- In Robusta's UI, verify the alert appears with the expected details.

docs/configuration/index.rst

@@ -77,6 +77,11 @@ Other
         :link: alertmanager-integration/dynatrace
         :link-type: doc
 
+    .. grid-item-card:: :octicon:`pulse;1em;` GCP Cloud Monitoring
+        :class-card: sd-bg-light sd-bg-text-light
+        :link: alertmanager-integration/gcp-monitoring
+        :link-type: doc
+
     .. grid-item-card:: :octicon:`pulse;1em;` Nagios
         :class-card: sd-bg-light sd-bg-text-light
         :link: alertmanager-integration/nagios

docs/index.rst

@@ -40,6 +40,7 @@
    Dynatrace <configuration/alertmanager-integration/dynatrace>
    Embedded Prometheus Stack <configuration/alertmanager-integration/embedded-prometheus>
    Google Managed Prometheus <configuration/alertmanager-integration/google-managed-prometheus>
+   GCP Cloud Monitoring <configuration/alertmanager-integration/gcp-monitoring>
    Grafana - Self-Hosted <configuration/alertmanager-integration/grafana-self-hosted>
    Grafana Cloud <configuration/alertmanager-integration/grafana-cloud>
    Nagios <configuration/alertmanager-integration/nagios>