Add DB config validation for required username on postgres/mysql

internal/infrastructure/persistence/gorm/db.go

@@ -23,8 +23,23 @@ type Config struct {
 	SSLMode  string
 }
 
+// Validate checks that the configuration is valid for the specified driver.
+// For postgres and mysql drivers, username must not be empty.
+func (c Config) Validate() error {
+	switch c.Driver {
+	case "postgres", "mysql":
+		if c.Username == "" {
+			return fmt.Errorf("username is required for %s driver", c.Driver)
+		}
+	}
+	return nil
+}
+
 // NewDB creates a new GORM database connection based on the configuration.
 func NewDB(cfg Config) *gorm.DB {
+	if err := cfg.Validate(); err != nil {
+		panic(err)
+	}
 	driver := cfg.Driver
 	switch driver {
 	case "postgres":

internal/infrastructure/persistence/gorm/db_test.go

@@ -0,0 +1,81 @@
+package gorm
+
+import (
+	"testing"
+)
+
+func TestConfigValidate(t *testing.T) {
+	tests := []struct {
+		name    string
+		config  Config
+		wantErr bool
+	}{
+		{
+			name: "postgres with username",
+			config: Config{
+				Driver:   "postgres",
+				Host:     "localhost",
+				Port:     5432,
+				Username: "testuser",
+				Password: "testpass",
+				DbName:   "testdb",
+				SSLMode:  "disable",
+			},
+			wantErr: false,
+		},
+		{
+			name: "postgres without username",
+			config: Config{
+				Driver:   "postgres",
+				Host:     "localhost",
+				Port:     5432,
+				Username: "",
+				Password: "testpass",
+				DbName:   "testdb",
+				SSLMode:  "disable",
+			},
+			wantErr: true,
+		},
+		{
+			name: "mysql with username",
+			config: Config{
+				Driver:   "mysql",
+				Host:     "localhost",
+				Port:     3306,
+				Username: "testuser",
+				Password: "testpass",
+				DbName:   "testdb",
+			},
+			wantErr: false,
+		},
+		{
+			name: "mysql without username",
+			config: Config{
+				Driver:   "mysql",
+				Host:     "localhost",
+				Port:     3306,
+				Username: "",
+				Password: "testpass",
+				DbName:   "testdb",
+			},
+			wantErr: true,
+		},
+		{
+			name: "sqlite without username (allowed)",
+			config: Config{
+				Driver: "sqlite",
+				DbName: "test.db",
+			},
+			wantErr: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := tt.config.Validate()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Config.Validate() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}