Summary

Document the serialization backends, schema validation system, and policy-based container configuration in container_system.

Parent Issue

Part of: [EPIC] docs: Address documentation gaps across all ecosystem systems (kcenon/common_system#325)

Background (Why)

container_system includes three undocumented subsystems:

1. Serializers — Including msgpack_serializer.h beyond the documented JSON/binary formats
2. Schema — Runtime schema validation for container structure at core/container/schema.h
3. Policy containers — Policy-based container configuration at core/policy_container.h + core/storage_policy.h

Users are unaware of MessagePack serialization support, schema validation capabilities, or policy-based container customization.

Source files:

• core/serializers/msgpack_serializer.h — MessagePack serialization
• core/container/schema.h — Schema definition and validation
• core/policy_container.h — Policy-based container configuration
• core/storage_policy.h — Storage strategy policies

Scope (What)

1. Serialization Framework

Available Serializers

MessagePack Serializer (msgpack_serializer.h)

• API: serialize/deserialize interface
• Type mapping (container types ↔ msgpack types)
• Nested container handling
• Binary data handling
• Performance comparison with JSON and binary serializers

2. Schema System (schema.h)

Schema Definition

• How to define expected container structure
• Supported type constraints
• Nested schema support
• Optional vs required fields

Schema Validation

• Runtime validation API
• Error reporting (which field, what violation)
• Validation performance impact

auto schema = container_schema::create()
    .field("name", type::string, required)
    .field("age", type::integer, optional)
    .field("address", nested_schema, required)
    .build();

auto result = schema.validate(my_container);

3. Policy Container Framework

policy_container (policy_container.h)

• How policies compose container behavior
• Available policy dimensions
• Compile-time vs runtime policy application

Storage Policies (storage_policy.h)

• Available storage strategies (in-memory, mapped, etc.)
• Policy selection criteria
• Custom storage policy interface

4. Integration Examples

• MessagePack serialization with schema validation
• Policy container with custom storage
• Full pipeline: create → validate → serialize → store

Acceptance Criteria

• MessagePack serializer fully documented with API and examples
• Schema system documented with definition and validation examples
• Policy container framework documented
• Storage policies listed with characteristics
• Performance comparison table for serializers
• Integration examples showing combined usage