Metadata schema system is the core system in Unified Catalog to describe the entities, including memory structure, on-wire format and storage layout.

This umbrella issue tracks the whole design and implementation of Unified Catalog' schema system, including:

1. Metadata entity design & implement.
2. Entity serialization and deserialization protocol design & implement.
3. Entity storage layout design & implement.

Subtasks are listed here:

• Metadata and Type Spec design ( lakehouse, zone, table, column and other basic entities), including memory structure, on-wire and storage layout design. [SUBTASK] Metadata and Type Spec design #11
• Metadata and Type Spec implementation (memory structure). [Subtask] Metadata and Type Spec Implementation #12
• Metadata on-wire protocol implement. [Subtask] Implement the on-wire protocol for Schema System #16
• Medata storage layout implement. [Subtask] Add Metadata Schema System protobuf Serde support #21