feat: add source and target database type fields

Add source_db_type and target_db_type to the migration config so the same binary can drive any supported direction.

internal/app/db-wrapper/main.go

@@ -0,0 +1,19 @@
+package dbwrapper
+
+import "fmt"
+
+type Factory func() DbWrapper
+
+var drivers = make(map[string]Factory)
+
+func Register(name string, factory Factory) {
+	drivers[name] = factory
+}
+
+func New(driverType string) (DbWrapper, error) {
+	factory, ok := drivers[driverType]
+	if !ok {
+		return nil, fmt.Errorf("driver not yet supported: %s", driverType)
+	}
+	return factory(), nil
+}