feat(core): add shared DTOs, MqttTopics constants, DatabaseBootstrapper, and ManagedMqttClient extensions

FinlyticCore/Database/DatabaseBootstrapper.cs

@@ -0,0 +1,79 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Npgsql;
+
+namespace FinlyticCore.Database;
+
+/// <summary>
+/// Utility for auto-bootstrapping PostgreSQL databases in a multi-service architecture.
+/// Ensures the target catalog database exists prior to EF Core connection and migration execution.
+/// </summary>
+public static class DatabaseBootstrapper
+{
+    /// <summary>
+    /// Checks if the target PostgreSQL database exists. If not, connects to the default administrative
+    /// database ('postgres') and executes CREATE DATABASE so that EF Core migrations can succeed.
+    /// </summary>
+    public static async Task EnsureDatabaseCreatedAsync(
+        string connectionString, 
+        ILogger? logger = null, 
+        CancellationToken cancellationToken = default)
+    {
+        if (string.IsNullOrWhiteSpace(connectionString)) return;
+
+        try
+        {
+            var builder = new NpgsqlConnectionStringBuilder(connectionString);
+            string targetDb = builder.Database ?? string.Empty;
+
+            if (string.IsNullOrWhiteSpace(targetDb) || string.Equals(targetDb, "postgres", StringComparison.OrdinalIgnoreCase))
+            {
+                return;
+            }
+
+            // Temporarily connect to the default 'postgres' database to query pg_database
+            builder.Database = "postgres";
+            string adminConnStr = builder.ConnectionString;
+
+            await using var conn = new NpgsqlConnection(adminConnStr);
+            await conn.OpenAsync(cancellationToken);
+
+            await using var checkCmd = new NpgsqlCommand(
+                "SELECT 1 FROM pg_database WHERE datname = @dbname;", conn);
+            checkCmd.Parameters.AddWithValue("dbname", targetDb);
+            var exists = await checkCmd.ExecuteScalarAsync(cancellationToken);
+
+            if (exists == null || exists == DBNull.Value)
+            {
+                logger?.LogInformation("[DatabaseBootstrapper] Database '{TargetDb}' does not exist on PostgreSQL host. Creating it automatically...", targetDb);
+                
+                // CREATE DATABASE cannot be executed as a parameterized identifier
+                await using var createCmd = new NpgsqlCommand(
+                    $"CREATE DATABASE \"{targetDb.Replace("\"", "\"\"")}\";", conn);
+                await createCmd.ExecuteNonQueryAsync(cancellationToken);
+                
+                logger?.LogInformation("[DatabaseBootstrapper] Successfully created database '{TargetDb}'.", targetDb);
+            }
+        }
+        catch (Exception ex)
+        {
+            logger?.LogWarning(ex, "[DatabaseBootstrapper] Auto-creation check failed or skipped for connection. Continuing with migration.");
+        }
+    }
+
+    /// <summary>
+    /// Combines catalog database auto-creation and EF Core Migration execution in a single call.
+    /// </summary>
+    public static async Task MigrateWithBootstrapAsync<TContext>(
+        this TContext context, 
+        string connectionString, 
+        ILogger? logger = null, 
+        CancellationToken cancellationToken = default) where TContext : DbContext
+    {
+        await EnsureDatabaseCreatedAsync(connectionString, logger, cancellationToken);
+        await context.Database.MigrateAsync(cancellationToken);
+    }
+}