feat: first doc for gateway

docs/documentation/platform/gateways/overview.mdx

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+---
+title: "Gateway"
+sidebarTitle: "Overview"
+description: "Learn how to provide access on private resources to Infisical."
+---
+
+<Info>
+    Note that Gateway is a paid feature.
+
+    If you're using Infisical Cloud, then it is available under the **Enterprise Tier**
+    If you're self-hosting Infisical, then you should contact sales@infisical.com to purchase an enterprise license to use it.
+
+</Info>
+
+## Introduction
+
+Gateway is Infisical's solution for providing secure access to your private resources without exposing them to the internet.
+
+By "without exposing," we mean that your resources remain completely closed to inbound connections - no SSH ports, no TCP ports are open.
+This level of security ensures that even port scanning cannot detect your resources.
+
+## How It Works
+
+A gateway is a simple server that acts as a bridge for direct communication between the Infisical server and your private, closed resources (such as databases).
+
+When deployed, the gateway establishes a connection with the relay server. Infisical then communicates with your gateway through these relays.
+All communication between Infisical and the gateway is end-to-end encrypted, ensuring that only the platform and your gateway can decrypt the transmitted information.
+
+## Deployment
+
+You can easily deploy a gateway using the Infisical CLI by following these steps:
+
+<Steps>
+  <Step title="Create a Gateway Identity">
+    1. Navigate to your **Organization Access Control**. 
+    2. Create a dedicated identity for the gateway. 
+    3. Best practice: Use one unique identity per gateway.
+    ![create-gateway](../../../images/platform/gateways/create-identity-for-gateway.png)
+  </Step>
+  
+  <Step title="Configure Authentication Method">
+    Set up authentication by following the [Identity Auth Method Configuration](../identities/universal-auth) guide.
+  </Step>
+
+  <Step title="Deploy the Gateway">
+    1. Deploy the gateway using Infisical CLI with this command: 
+    ```bash
+    INFISICAL_TOKEN=$(infisical login ...) infisical gateway 
+    ```
+  <Note>
+    Verify that the deployed gateway has access to your private resources
+  </Note>
+
+  </Step>
+  <Step title="Verification">
+    1. Check the gateway log to have **Gateway started successfully**
+    
+    2. Navigate to **Gateways** list page in Org Access Control
+    ![list-gateway](../../../images/platform/gateways/gateway-list.png)
+  </Step>
+</Steps>
+
+## Using Your Gateway
+
+### Configuring Dynamic Secrets
+
+To use your gateway with dynamic secrets:
+
+1. Navigate to your dynamic secret provider settings
+2. Under **Gateway** options, switch from **Internet Gateway** to your deployed gateway
+   ![dynamic-secret-gateway](../../../images/platform/gateways/dynamic-secret.png)
+
+### Supported Providers
+
+Currently, gateways are supported for the following dynamic secret providers:
+
+- SQL Database Providers (MySQL, PostgreSQL, etc.)
+
+<Note>Additional provider support will be added in future updates.</Note>