Update XML doc comment in backend projects

web/backend/Infrastructure/Infrastructure.Email.Templates/Rendering/EmailTemplateProvider.cs

@@ -12,6 +12,7 @@ namespace Infrastructure.Email.Templates.Rendering;
 public class EmailTemplateProvider(IServiceProvider serviceProvider, ILoggerFactory loggerFactory)
     : IEmailTemplateProvider
 {
+    /// <inheritdoc/>
     public async Task<string> RenderUserRegisteredEmailAsync(
         string username,
         string confirmationLink
@@ -26,6 +27,7 @@ public class EmailTemplateProvider(IServiceProvider serviceProvider, ILoggerFact
         return await RenderComponentAsync<UserRegistration>(parameters);
     }
 
+    /// <inheritdoc/>
     public async Task<string> RenderResendConfirmationEmailAsync(
         string username,
         string confirmationLink

web/backend/Infrastructure/Infrastructure.Email.Templates/Rendering/IEmailTemplateProvider.cs

@@ -5,13 +5,15 @@ namespace Infrastructure.Email.Templates.Rendering;
 /// </summary>
 public interface IEmailTemplateProvider
 {
-    /// <summary>
-    ///     Renders the UserRegisteredEmail template.
-    /// </summary>
+    /// <summary>Renders the registration confirmation email template.</summary>
+    /// <param name="username">The recipient's username, shown in the greeting.</param>
+    /// <param name="confirmationLink">The URL the recipient follows to confirm their account.</param>
+    /// <returns>A task whose result is the rendered HTML for the email body.</returns>
     Task<string> RenderUserRegisteredEmailAsync(string username, string confirmationLink);
 
-    /// <summary>
-    ///     Renders the ResendConfirmation template.
-    /// </summary>
+    /// <summary>Renders the resend-confirmation email template.</summary>
+    /// <param name="username">The recipient's username, shown in the greeting.</param>
+    /// <param name="confirmationLink">The URL the recipient follows to confirm their account.</param>
+    /// <returns>A task whose result is the rendered HTML for the email body.</returns>
     Task<string> RenderResendConfirmationEmailAsync(string username, string confirmationLink);
 }

web/backend/Infrastructure/Infrastructure.Email/IEmailProvider.cs

@@ -5,7 +5,17 @@ namespace Infrastructure.Email;
 /// </summary>
 public interface IEmailProvider
 {
+    /// <summary>Sends an email to a single recipient.</summary>
+    /// <param name="to">The recipient's email address.</param>
+    /// <param name="subject">The email subject line.</param>
+    /// <param name="body">The email body content.</param>
+    /// <param name="isHtml">Whether <paramref name="body"/> is HTML; when <see langword="false"/> it is sent as plain text.</param>
     Task SendAsync(string to, string subject, string body, bool isHtml = true);
 
+    /// <summary>Sends an email to multiple recipients.</summary>
+    /// <param name="to">The recipients' email addresses.</param>
+    /// <param name="subject">The email subject line.</param>
+    /// <param name="body">The email body content.</param>
+    /// <param name="isHtml">Whether <paramref name="body"/> is HTML; when <see langword="false"/> it is sent as plain text.</param>
     Task SendAsync(IEnumerable<string> to, string subject, string body, bool isHtml = true);
 }

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

@@ -51,15 +51,17 @@ public class SmtpEmailProvider : IEmailProvider
         _fromName = Environment.GetEnvironmentVariable("SMTP_FROM_NAME") ?? "The Biergarten";
     }
 
+    /// <inheritdoc/>
     public async Task SendAsync(string to, string subject, string body, bool isHtml = true)
     {
         await SendAsync([to], subject, body, isHtml);
     }
 
-    /// <summary>
+    /// <inheritdoc/>
+    /// <remarks>
     ///     Connects using StartTls when SSL is enabled (or no encryption otherwise), authenticates
     ///     if credentials were configured, sends the message, and disconnects.
-    /// </summary>
+    /// </remarks>
     /// <exception cref="InvalidOperationException">
     ///     Thrown when connecting, authenticating, or sending via SMTP fails, wrapping the original exception.
     /// </exception>

web/backend/Infrastructure/Infrastructure.Sql/DependencyInjection/InfrastructureSqlServiceCollectionExtensions.cs

@@ -2,8 +2,11 @@ using Microsoft.Extensions.DependencyInjection;
 
 namespace Infrastructure.Sql.DependencyInjection;
 
+/// <summary>Extension methods for registering SQL infrastructure services with dependency injection.</summary>
 public static class InfrastructureSqlServiceCollectionExtensions
 {
+    /// <summary>Registers <see cref="DefaultSqlConnectionFactory" /> as a singleton <see cref="ISqlConnectionFactory" />.</summary>
+    /// <returns>The same <paramref name="services" /> instance, for chaining.</returns>
     public static IServiceCollection AddInfrastructureSql(this IServiceCollection services)
     {
         services.AddSingleton<ISqlConnectionFactory, DefaultSqlConnectionFactory>();

web/backend/Infrastructure/Infrastructure.Sql/SqlErrorCodes.cs

@@ -1,15 +1,18 @@
 namespace Infrastructure.Sql;
 
 /// <summary>
-///     Custom SQL Server error numbers (50000+) that this application's stored procedures use to
-///     signal domain-level failures via <c>THROW</c>. Repositories catch
-///     <see cref="Microsoft.Data.SqlClient.SqlException" /> and switch on <c>ex.Number</c> against
-///     these constants to translate the failure into the corresponding <c>Domain.Exceptions</c> type.
+///     Custom SQL Server error numbers (50000+) that a stored procedure could use to signal
+///     domain-level failures via <c>THROW</c>, for a repository to catch as
+///     <see cref="Microsoft.Data.SqlClient.SqlException" /> and translate via <c>ex.Number</c> into
+///     the corresponding <c>Domain.Exceptions</c> type.
 /// </summary>
 /// <remarks>
-///     Each number is shared by every procedure that raises that category of error — it identifies
-///     the category, not a single call site. The procedure's own error message (<c>ex.Message</c>)
-///     already says which entity or rule was involved, so it is safe to surface directly to callers.
+///     Currently unused: the schema has no stored procedures, and no repository throws or catches on
+///     these numbers. Repositories instead run their own existence/concurrency checks and throw
+///     <c>Domain.Exceptions</c> directly (see <c>docs/website/database.md</c> for the current
+///     approach). This type is kept in case a future stored procedure reintroduces the pattern; each
+///     number would
+///     identify a category of error shared by every procedure that raises it, not a single call site.
 /// </remarks>
 public static class SqlErrorCodes
 {