[Task]: Define Redis governance serialization strategy

[rian-be]

Summary

Add dedicated serialization layer for Redis backed governed mutation requests so request documents, metadata values, and provider payloads can be written and read consistently.

Goal

Make Redis payload handling explicit, reusable, and compatible with the governance request model instead of scattering JSON serialization details across persistence and query code.

Scope

What should be implemented?

• Add the ModularityKit.Mutator.Governance.Redis.Serialization area for Redis payload handling
• Define centralized request serialization for MutationRequest documents
• Support deserialization back into the governance request model
• Handle flexible metadata values consistently in Redis payloads
• Support serialization of read only collection shapes used by governance models
• Keep Redis payload handling reusable across persistence and query paths
• Keep serialization decisions internal to the Redis provider boundary
• Document serialization and compatibility decisions in provider docs and ADRs where needed

Acceptance Criteria

• Redis request payload serialization is centralized instead of duplicated
• Request documents round-trip without losing governance semantics
• Flexible metadata values are handled consistently during serialization and deserialization
• Provider serialization supports the collection shapes used by governance models
• Persistence and query code reuse the same payload handling path
• Serialization compatibility decisions are documented for future provider evolution

Notes

Redis backed governance depends on stable document format. Serialization is not just an implementation detail here; it defines how request data survives round trips, how metadata remains usable, and how future package versions can evolve safely.

This should align with the Redis provider architecture and document compatibility ADRs.

Related ADRs:

• ADR-029: Governance Redis Provider Package
• ADR-030: Governance Redis Request Storage and Query Strategy
• ADR-031: Governance Redis Serialization and Document Compatibility