update the alerting-example-telegram.md docs (#180)

* create the alerting example- Telegram doc

* update the alerting example - telegram doc

Author: DebashisBorgohainO2

docs/user-guide/alerts/.pages

@@ -6,3 +6,4 @@ nav:
     - Import and Export Alerts: import-export-alerts.md
     - Multi-window Selector in Scheduled Alerts (SQL Mode): multi-window-selector-scheduled-alerts-concept.md
     - Use Multi-window Selector in Scheduled Alerts: how-to-access-multi-window-selector-scheduled-alerts.md
+    - Use Telegram for Alerts: alerting-example-telegram.md

docs/user-guide/alerts/alerting-example-telegram.md

@@ -0,0 +1,82 @@
+This guide explains how to configure [OpenObserve alerts]() to send notifications directly to Telegram. You will create a template, configure an alert destination, and attach it to an alert rule.
+
+## Configure OpenObserve alerts
+??? "Prerequisites"
+    - A Telegram account
+    - Telegram bot token: Create a bot in Telegram using **BotFather**. BotFather provides the token.
+    - Telegram chat ID: Start a chat with your bot, send a message, and run `getUpdates` with your bot token to retrieve the `chat.id`.
+
+    Verify the bot token and chat ID with the following commands:
+
+    **Get updates**
+    ```bash
+    curl "https://api.telegram.org/bot<YOUR_BOT_TOKEN>/getUpdates"
+    ```
+
+    **Get bot details**
+    ```bash
+    curl "https://api.telegram.org/bot<YOUR_BOT_TOKEN>/getMe"
+    ```
+
+    **Send a test message**
+    ```bash
+    set TOKEN=<YOUR_BOT_TOKEN>
+    set CHAT=<YOUR_CHAT_ID>
+
+    curl.exe -X POST "https://api.telegram.org/bot%TOKEN%/sendMessage" ^
+      --data-urlencode "chat_id=%CHAT%" ^
+      --data-urlencode "text=OpenObserve test"
+    ```
+    If the message appears in Telegram, your setup is correct.
+
+??? "Step 1: Create Template"
+    1. Go to **Management > Templates > Add Template**.
+    2. Enter a name, for example `Telegram_alert`.
+    3. Select **Web Hook**.
+    4. In the Body, add the following JSON. Replace <YOUR_CHAT_ID> with your chat ID.
+    ![Create Template](alerting-telegram-template.png)
+    5. Save the template.
+
+??? "Step 2: Create Alert Destination"
+    1. Go to **Management > Alert Destinations > Add Destination**.
+    2. Enter a name, for example `Telegram_alert`.
+    3. Select the template you created earlier (Telegram_alert).
+    4. Set **URL** to: https://api.telegram.org/bot<YOUR_BOT_TOKEN>/sendMessage
+    5. Set **Method** to POST.
+    6. Add the header: Content-Type = application/json
+    7. Save the destination.
+    ![Create Alert Destination](alerting-telegram-destination.png)
+
+??? "Step 3: Create Alert"
+    1. Go to **Alerts > Add Alert**.
+    2. Configure the alert:
+        
+        - Name: any name
+        - Stream Type: logs
+        - Stream Name: select your stream. For example, default.
+        - Alert Type: Scheduled
+        - Condition: for example service_name = ingress-nginx
+        ![Config Alert](alerting-telegram-config.png)
+        - Threshold: >= 1 time
+        - Period: 1 minute
+        - Frequency: 1 minute
+        - Destination: select `Telegram_alert`
+        ![Config Alert](alerting-telegram-config-conditions.png)
+        - In Row Template, define the row format, for example: `Alert was active at {_timestamp}`
+    3. Save the alert.
+
+??? "Step 4: Verify alert delivery"
+    After you save the alert, wait until the condition is met.
+    If configured correctly, you will receive a message in Telegram that looks similar to the following:
+    ![Verify alert delivery](alerting-telegram-alert-delivery.png)
+
+??? "Troubleshooting"
+    **Issue:** No message received in Telegram <br>
+    **Solution:** Verify that the template body includes a valid `chat_id`. Without `chat_id`, Telegram cannot deliver the message.
+
+    Example of a valid body:
+
+    {
+      "chat_id": "8237******",
+      "text": "{alert_name} is active \nDetails:\n{rows}"
+    }