add xmldoc comments

web/backend/Infrastructure/Infrastructure.Email/SmtpEmailProvider.cs

@@ -18,6 +18,25 @@ public class SmtpEmailProvider : IEmailProvider
     private readonly string _fromEmail;
     private readonly string _fromName;
 
+    /// <summary>
+    /// Initializes a new instance of <see cref="SmtpEmailProvider"/>, reading SMTP configuration
+    /// from environment variables.
+    /// </summary>
+    /// <remarks>
+    /// Reads the following environment variables:
+    /// <list type="bullet">
+    /// <item><description><c>SMTP_HOST</c> (required) - the SMTP server hostname.</description></item>
+    /// <item><description><c>SMTP_PORT</c> (optional, default "587") - the SMTP server port, must be a valid integer.</description></item>
+    /// <item><description><c>SMTP_USERNAME</c> (optional) - the username used for authentication.</description></item>
+    /// <item><description><c>SMTP_PASSWORD</c> (optional) - the password used for authentication.</description></item>
+    /// <item><description><c>SMTP_USE_SSL</c> (optional, default "true") - whether to use StartTls when connecting.</description></item>
+    /// <item><description><c>SMTP_FROM_EMAIL</c> (required) - the email address used as the sender.</description></item>
+    /// <item><description><c>SMTP_FROM_NAME</c> (optional, default "The Biergarten") - the display name used as the sender.</description></item>
+    /// </list>
+    /// </remarks>
+    /// <exception cref="InvalidOperationException">
+    /// Thrown when <c>SMTP_HOST</c> or <c>SMTP_FROM_EMAIL</c> is not set, or when <c>SMTP_PORT</c> is not a valid integer.
+    /// </exception>
     public SmtpEmailProvider()
     {
         _host =
@@ -53,6 +72,14 @@ public class SmtpEmailProvider : IEmailProvider
             ?? "The Biergarten";
     }
 
+    /// <summary>
+    /// Sends an email to a single recipient by delegating to the multi-recipient overload.
+    /// </summary>
+    /// <param name="to">Recipient email address</param>
+    /// <param name="subject">Email subject line</param>
+    /// <param name="body">Email body (HTML or plain text)</param>
+    /// <param name="isHtml">Whether the body is HTML (default: true)</param>
+    /// <exception cref="InvalidOperationException">Thrown when connecting, authenticating, or sending via SMTP fails.</exception>
     public async Task SendAsync(
         string to,
         string subject,
@@ -63,6 +90,16 @@ public class SmtpEmailProvider : IEmailProvider
         await SendAsync([to], subject, body, isHtml);
     }
 
+    /// <summary>
+    /// Sends an email to multiple recipients using MailKit's <see cref="SmtpClient"/>.
+    /// Connects using StartTls when SSL is enabled (or no encryption otherwise), authenticates
+    /// if credentials were configured, sends the message, and disconnects.
+    /// </summary>
+    /// <param name="to">List of recipient email addresses</param>
+    /// <param name="subject">Email subject line</param>
+    /// <param name="body">Email body (HTML or plain text)</param>
+    /// <param name="isHtml">Whether the body is HTML (default: true)</param>
+    /// <exception cref="InvalidOperationException">Thrown when connecting, authenticating, or sending via SMTP fails. The original exception is included as the inner exception.</exception>
     public async Task SendAsync(
         IEnumerable<string> to,
         string subject,