Add user profile and avatar upload feature

web/backend/Features/Features.Users/Repository/UserProfileRepository.cs

@@ -0,0 +1,65 @@
+using System.Data.Common;
+using Dapper;
+using Database.Connection;
+
+namespace Features.Auth.Repository;
+
+/// <summary>
+///     Dapper-based implementation of <see cref="IUserProfileRepository" />.
+/// </summary>
+public class UserProfileRepository(ISqlConnectionFactory connectionFactory)
+    : DapperRepository(connectionFactory),
+        IUserProfileRepository
+{
+    /// <inheritdoc />
+    public async Task<Guid> GetOrCreateProfileIdAsync(
+        Guid userAccountId,
+        CancellationToken cancellationToken
+    )
+    {
+        await using DbConnection connection = await CreateConnection();
+        await using DbTransaction transaction = await connection.BeginTransactionAsync();
+
+        try
+        {
+            // UPDLOCK/HOLDLOCK: AK_UserProfile_UserAccountID is composite with UserProfileID, so it
+            // doesn't by itself stop two concurrent callers from creating duplicate profiles for the
+            // same account; holding the lock through the transaction serializes them instead.
+            Guid? userProfileId = await connection.ExecuteScalarAsync<Guid?>(
+                new CommandDefinition(
+                    """
+                    SELECT UserProfileID
+                    FROM dbo.UserProfile WITH (UPDLOCK, HOLDLOCK)
+                    WHERE UserAccountID = @UserAccountId
+                    """,
+                    new { UserAccountId = userAccountId },
+                    transaction
+                )
+            );
+
+            if (userProfileId is null)
+            {
+                userProfileId = Guid.NewGuid();
+
+                await connection.ExecuteAsync(
+                    new CommandDefinition(
+                        """
+                        INSERT INTO dbo.UserProfile (UserProfileID, Biography, UserAccountID)
+                        VALUES (@UserProfileId, '', @UserAccountId)
+                        """,
+                        new { UserProfileId = userProfileId, UserAccountId = userAccountId },
+                        transaction
+                    )
+                );
+            }
+
+            await transaction.CommitAsync(cancellationToken);
+            return userProfileId.Value;
+        }
+        catch
+        {
+            await RollbackQuietlyAsync(transaction);
+            throw;
+        }
+    }
+}