Message Store Generator

[GenerateMessageStore] creates a typed MessageStore<TPayload> factory for a partial class or struct.

[GenerateMessageStore(typeof(OrderSubmitted), FactoryName = "Create", StoreName = "order-audit")]
public static partial class OrderAuditStore
{
    [MessageStoreIdentity]
    private static string Identity(Message<OrderSubmitted> message, MessageContext context)
        => message.Headers.MessageId!;

    [MessageStoreRetention]
    private static bool Retain(StoredMessage<OrderSubmitted> stored)
        => !stored.Message.Payload.ContainsSensitiveData;
}

The generated factory composes the fluent runtime API:

• MessageStore<TPayload>.Create(StoreName)
• optional .IdentifyBy(...)
• optional .RetainWhen(...)
• .Build()

Diagnostics:

• PKMS001: host type must be partial.
• PKMS002: identity method must be static string Method(Message<TPayload>, MessageContext).
• PKMS003: retention method must be static bool Method(StoredMessage<TPayload>).
• PKMS004: only one identity hook and one retention hook are allowed.