Added the catalogue models and seed to support phase 3 of the POC prototype in the Persistence package.

Packages/Persistence/Sources/Internal/Models/OfferRecord.swift

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+import FluentKit
+import Foundation
+
+/// A FluentKit model of a single `offers` row.
+final class OfferRecord: Model, @unchecked Sendable {
+
+    // MARK: Properties
+
+    static let schema = "offers"
+
+    @ID(key: .id)
+    var id: UUID?
+
+    @Parent(key: "conversation_id")
+    var conversation: ConversationRecord
+
+    @Parent(key: "listing_id")
+    var listing: ListingRecord
+
+    @Parent(key: "buyer_id")
+    var buyer: UserRecord
+
+    @Field(key: "amount_cents")
+    var amountCents: Int
+
+    @Field(key: "status")
+    var status: String
+
+    @Field(key: "created_at")
+    var createdAt: Date
+
+    @Field(key: "expires_at")
+    var expiresAt: Date
+
+    // MARK: Initializers
+
+    init() {}
+
+    init(
+        conversationID: UUID,
+        listingID: UUID,
+        buyerID: UUID,
+        amountCents: Int,
+        at date: Date
+    ) {
+        self.$conversation.id = conversationID
+        self.$listing.id = listingID
+        self.$buyer.id = buyerID
+        self.amountCents = amountCents
+        self.status = Offer.Status.open.rawValue
+        self.createdAt = date
+        self.expiresAt = date.addingTimeInterval(Offer.lifetime)
+    }
+
+}
+
+// MARK: - Extensions
+
+extension OfferRecord {
+
+    // MARK: Methods
+
+    /// The `Sendable` snapshot of the saved record; its buyer, and its listing with its shop, must be eager-loaded.
+    /// - Parameter now: the moment an open offer's expiry is judged at.
+    func snapshot(
+        at now: Date
+    ) throws -> Offer {
+        let stored = Offer.Status(rawValue: status) ?? .declined
+
+        return .init(
+            id: try requireID(),
+            conversationID: $conversation.id,
+            listing: listing.snapshot,
+            buyer: try buyer.snapshot,
+            amountCents: amountCents,
+            status: stored == .open && expiresAt <= now ? .expired : stored,
+            createdAt: createdAt,
+            expiresAt: expiresAt
+        )
+    }
+
+}