Feat: Konnect metering and billing Subjects

app/_data/schemas/frontmatter/base.json

@@ -43,7 +43,7 @@
       "type": "array",
       "items": {
         "type": "string",
-        "enum": ["ai-gateway", "gateway", "insomnia", "mesh", "kic", "catalog", "advanced-analytics", "dev-portal", "operator", "konnect", "event-gateway", "konnect-reference-platform"]
+        "enum": ["ai-gateway", "gateway", "insomnia", "mesh", "kic", "catalog", "advanced-analytics", "dev-portal", "operator", "konnect", "event-gateway", "konnect-reference-platform", "metering-and-billing"]
       }
     },
     "tools": {

app/_indices/metering-and-billing.yaml

@@ -0,0 +1,12 @@
+title: Metering and Billing Documentation Index
+sections:
+  - title: Reference
+    items:
+      - path: /metering-and-billing/
+      - path: /metering-and-billing/**/*
+    auto_exclude: true
+  - title: How-Tos
+    items:
+      - type: how-to
+        products:
+          - metering-and-billing

app/_landing_pages/metering-and-billing.yaml

@@ -0,0 +1,14 @@
+metadata:
+  title: "Metering and Billing"
+  content_type: landing_page
+  description: Learn about managing service meshes and control planes with Metering and Billing.
+  breadcrumbs:
+    - /metering-and-billing/
+  products:
+    - metering-and-billing
+
+rows:
+  - header:
+      type: h1
+      text: "Metering and Billing"
+      sub_text: Manage all of your {{site.mesh_product_name}} service meshes in a single console

app/metering-and-billing/subjects.md

@@ -0,0 +1,84 @@
+---
+title: "Subjects"
+content_type: reference
+description: "Learn how subjects work in {{site.konnect_short_name}} Metering and Billing and how they relate to usage tracking and external billing systems."
+layout: reference
+products:
+  - metering-and-billing
+tools:
+    - konnect-api
+works_on:
+  - konnect
+breadcrumbs:
+  - /metering-and-billing/
+related_resources:
+  - text: "{{site.konnect_short_name}} Metering and Billing"
+    url: /metering-and-billing/
+
+---
+
+## What is a subject?
+
+Subjects represent the entity that produces usage in {{site.konnect_short_name}} Metering and Billing.
+
+A subject can represent any unique event in your system, such as: 
+* Customer ID or User ID  
+* Hostname or IP address  
+* Service or application name  
+* Device ID  
+
+The subject model is intentionally generic, enabling flexible application across different metering scenarios.
+
+In most implementations, a subject maps 1:1 with a customer or user in your system.
+
+## How do subjects work?
+
+{{site.konnect_short_name}} Metering and Billing uses subjects to:
+
+* Associate usage with external systems (for example, Stripe or CRM tools)
+* Store descriptive metadata
+* Identify the entity producing metered events
+
+Each subject contains the following fields:
+
+* **Key** – The subject’s unique identifier  
+* **Display name** – A human-readable label shown in the UI  
+* **Metadata** – Optional key-value attributes for additional context  
+
+## Subjects and customers
+
+In most cases, subjects are related to metering and and create usage. A customer, is related to billing and pays for usage. 
+
+You can use the same identifier for both, but they can differ if your usage producer and billing entity are not the same.
+
+For example:
+
+* One customer may have multiple usage-producing subjects  
+* A single subject’s usage may need to be billed to a different customer  
+
+For more information, see **subject assignment** in the Metering and Billing documentation.
+
+## Data ingestion
+
+When shipping data to {{site.konnect_short_name}} you must include the subject within the payload: 
+
+```ts
+{
+  "specversion": "1.0",
+  "type": "api-calls",
+  "id": "00002",
+  "time": "2023-01-01T00:00:00.001Z",
+  "source": "service-0",
+  "subject": "customer-1",
+  "data": {...}
+}
+```
+
+
+## Schema
+
+[Insert Schema here](https://openmeter.io/docs/api/cloud#tag/subjects)
+
+## Set up a Route
+
+CRUD a subject here