feat(dbmanager): ✨ add support for existing SQL connections

* Introduced NewConnectionFromDB function to create connections from existing *sql.DB instances.
* Added ExistingDBProvider to wrap existing database connections for dbmanager features.
* Implemented tests for NewConnectionFromDB and ExistingDBProvider functionalities.

pkg/dbmanager/factory_test.go

@@ -0,0 +1,210 @@
+package dbmanager
+
+import (
+	"context"
+	"database/sql"
+	"testing"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func TestNewConnectionFromDB(t *testing.T) {
+	// Open a SQLite in-memory database
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	// Create a connection from the existing database
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	if conn == nil {
+		t.Fatal("Expected connection to be created")
+	}
+
+	// Verify connection properties
+	if conn.Name() != "test-connection" {
+		t.Errorf("Expected name 'test-connection', got '%s'", conn.Name())
+	}
+
+	if conn.Type() != DatabaseTypeSQLite {
+		t.Errorf("Expected type DatabaseTypeSQLite, got '%s'", conn.Type())
+	}
+}
+
+func TestNewConnectionFromDB_Connect(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	// Connect should verify the existing connection works
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Errorf("Expected Connect to succeed, got error: %v", err)
+	}
+
+	// Cleanup
+	conn.Close()
+}
+
+func TestNewConnectionFromDB_Native(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Get native DB
+	nativeDB, err := conn.Native()
+	if err != nil {
+		t.Errorf("Expected Native to succeed, got error: %v", err)
+	}
+
+	if nativeDB != db {
+		t.Error("Expected Native to return the same database instance")
+	}
+}
+
+func TestNewConnectionFromDB_Bun(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Get Bun ORM
+	bunDB, err := conn.Bun()
+	if err != nil {
+		t.Errorf("Expected Bun to succeed, got error: %v", err)
+	}
+
+	if bunDB == nil {
+		t.Error("Expected Bun to return a non-nil instance")
+	}
+}
+
+func TestNewConnectionFromDB_GORM(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Get GORM
+	gormDB, err := conn.GORM()
+	if err != nil {
+		t.Errorf("Expected GORM to succeed, got error: %v", err)
+	}
+
+	if gormDB == nil {
+		t.Error("Expected GORM to return a non-nil instance")
+	}
+}
+
+func TestNewConnectionFromDB_HealthCheck(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	// Health check should succeed
+	err = conn.HealthCheck(ctx)
+	if err != nil {
+		t.Errorf("Expected HealthCheck to succeed, got error: %v", err)
+	}
+}
+
+func TestNewConnectionFromDB_Stats(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-connection", DatabaseTypeSQLite, db)
+	ctx := context.Background()
+
+	err = conn.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+
+	stats := conn.Stats()
+	if stats == nil {
+		t.Fatal("Expected stats to be returned")
+	}
+
+	if stats.Name != "test-connection" {
+		t.Errorf("Expected stats.Name to be 'test-connection', got '%s'", stats.Name)
+	}
+
+	if stats.Type != DatabaseTypeSQLite {
+		t.Errorf("Expected stats.Type to be DatabaseTypeSQLite, got '%s'", stats.Type)
+	}
+
+	if !stats.Connected {
+		t.Error("Expected stats.Connected to be true")
+	}
+}
+
+func TestNewConnectionFromDB_PostgreSQL(t *testing.T) {
+	// This test just verifies the factory works with PostgreSQL type
+	// It won't actually connect since we're using SQLite
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	conn := NewConnectionFromDB("test-pg", DatabaseTypePostgreSQL, db)
+	if conn == nil {
+		t.Fatal("Expected connection to be created")
+	}
+
+	if conn.Type() != DatabaseTypePostgreSQL {
+		t.Errorf("Expected type DatabaseTypePostgreSQL, got '%s'", conn.Type())
+	}
+}