docs: Update use SendGrid as Email Provider instead of SMTP Server (#643)

* docs: Update use SendGrid as Email Provider instead of SMTP Server

* docs: fix link detected

Author: nb150301

docs/provider/email/sendgrid.md

@@ -1,36 +1,50 @@
 ---
 title: SendGrid
-description: Using SendGrid as the SMTP server
+description: Using SendGrid as an Email Provider
 keywords: [email, SendGrid]
 authors: [UsherFall]
 ---
 
-In this guide, we will be using SendGrid as the SMTP server.
+In this guide, we will use SendGrid as an email provider.
 
-### Step 1: Create API key for your SendGrid account
+## Step 1: Create an API Key for Your SendGrid Account
 
-Expand the **Settings** from the left navigation bar, click on the **API Keys** option from this list. Here, you will see all of your API keys if you have generated any in the past. To generate a new one, you need to click on **Create API Key** and pay attention to the permissions.
+Expand **Settings** from the left navigation bar, then click on **API Keys**. Here, you will see all previously generated API keys. To create a new one, click on **Create API Key** and configure the necessary permissions.
 
 ![sendgrid_apikey](/img/providers/sendgrid_apikey.png)
 
-### Step 2: Sender Verification
+## Step 2: Sender Verification
 
-Refer to the document to verify your email sender, you can choose **Single Sender Verification** or **Domain Authentication**: [Sender Identity](https://docs.sendgrid.com/for-developers/sending-email/sender-identity)
+To verify your email sender, choose between **Single Sender Verification** or **Domain Authentication** by referring to the official documentation:  
+[Sender Identity](https://docs.sendgrid.com/for-developers/sending-email/sender-identity)
 
-### Step 3: Configure Casdoor email Provider
+## Step 3: Configure Casdoor as an Email Provider
 
-Now create an email provider in Casdoor. Fill in the required fields below:
+Create a SendGrid email provider in Casdoor and fill in the following fields:
 
-| Required fields | Remark                    |
-|-----------------|---------------------------|
-| Username        | Enter "apikey"            |
-| Password        | Your SendGrid's API key   |
-| From Address    | Your verified sender      |
-| Host            | Enter "smtp.sendgrid.net" |
-| Port            | Default is 465            |
+### Required Fields
 
-![sendgrid_provider](/img/providers/sendgrid_provider.png)
+| Field         | Description                                |
+|--------------|--------------------------------------------|
+| Secret Key   | Your SendGrid API key                     |
+| From Address | Your verified email address (or domain)   |
 
-Click on the `Test SMTP Connection` button. If you see `provider: SMTP connected successfully`, it means that your Casdoor service can access the SendGrid service.
+### Default Fields
 
-Next, click on the `Send Testing Email` button. If you see `Email sent successfully`, it means that the test email has been sent successfully from the `From` address to the `Test Email`.
+| Field    | Description                          |
+|---------|--------------------------------------|
+| Endpoint | Default: `/v3/mail/send`            |
+| Host     | Default: `https://api.sendgrid.com` |
+
+### Email Fields
+
+| Field         | Description                               |
+|--------------|-------------------------------------------|
+| From Name    | The display name of the email sender     |
+| Email Title  | The subject of the email                 |
+| Email Content | Supports HTML templates                 |
+| Test Email   | The recipient's email address for testing |
+
+![sendgrid_email_provider_fields](/img/providers/sendgrid_email_provider_fields.png)
+
+Finally, click on the **Send Testing Email** button and check your `Test Email` address for the test email.