This PR implements a pure, algebraic schema migration system for ZIO Schema 2. It introduces a data-driven approach to migrating values between different schema versions using DynamicValue.

Changes

• Core Data Structures:
  • MigrationAction: Algebraic data type for atomic migration steps (AddField, DropField, Rename, TransformValue).
  • DynamicMigration: Sequence of actions executable on DynamicValue.
  • DynamicSchemaExpr: Serializable expression language for migration logic (logic, arithmetic, lookups).
• User API:
  • Migration[A, B]: Typed wrapper ensuring schema compatibility.
  • MigrationBuilder: Fluent API for constructing migrations.
• Execution:
  • Implemented evaluation logic for DynamicMigration and DynamicSchemaExpr.
  • Added comprehensive error handling via MigrationError.

Verification

• Added MigrationSpec to verify core scenarios:
  • Adding fields with default values.
  • Renaming fields in records.
• Verified compilation and test execution via sbt.

Related Issues

Closes #519

/claim #519