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

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

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+import FluentKit
+import Foundation
+
+/// A FluentKit model of a single `conversations` row: a buyer and a shop, talking about a listing or the shop at large.
+final class ConversationRecord: Model, @unchecked Sendable {
+
+    // MARK: Properties
+
+    static let schema = "conversations"
+
+    @ID(key: .id)
+    var id: UUID?
+
+    @Parent(key: "buyer_id")
+    var buyer: UserRecord
+
+    @Parent(key: "shop_id")
+    var shop: ShopRecord
+
+    @OptionalParent(key: "listing_id")
+    var listing: ListingRecord?
+
+    @Field(key: "created_at")
+    var createdAt: Date
+
+    /// When the buyer last opened the conversation; what came later is unread to them.
+    @Field(key: "buyer_read_at")
+    var buyerReadAt: Date
+
+    /// When the seller last opened the conversation; what came later is unread to them.
+    @Field(key: "seller_read_at")
+    var sellerReadAt: Date
+
+    @Children(for: \.$conversation)
+    var messages: [MessageRecord]
+
+    @Children(for: \.$conversation)
+    var offers: [OfferRecord]
+
+    @Children(for: \.$conversation)
+    var sales: [SaleRecord]
+
+    // MARK: Initializers
+
+    init() {}
+
+    init(
+        buyerID: UUID,
+        shopID: UUID,
+        listingID: UUID?,
+        at date: Date
+    ) {
+        self.$buyer.id = buyerID
+        self.$shop.id = shopID
+        self.$listing.id = listingID
+        self.createdAt = date
+        self.buyerReadAt = date
+        self.sellerReadAt = date
+    }
+
+}