Added the catalogue models and seed to support phase 1 of the POC prototype in the Persistence package.

Packages/Persistence/Sources/Public/Repositories/CatalogueRepository.swift

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+import FluentKit
+import HummingbirdFluent
+
+/// Reads the shops and their listings through the default database.
+public struct CatalogueRepository: Sendable {
+
+    // MARK: Properties
+
+    private let fluent: Fluent
+
+    // MARK: Initializers
+
+    /// Creates a repository backed by the given `Fluent` service.
+    /// - Parameter fluent: the service whose default database the repository operates on.
+    public init(
+        fluent: Fluent
+    ) {
+        self.fluent = fluent
+    }
+
+    // MARK: Methods
+
+    /// Fetches the listing with the given slug.
+    /// - Parameter slug: the listing's URL slug.
+    /// - Returns: the listing, or `nil` when none has the slug.
+    public func listing(
+        slug: String
+    ) async throws -> Listing? {
+        try await ListingRecord.query(on: fluent.db())
+            .filter(\.$slug == slug)
+            .with(\.$shop)
+            .first()?
+            .snapshot
+    }
+
+    /// Fetches the listings meeting the filter, in its order.
+    ///
+    /// The prototype filters in memory, which its few dozen seeded listings allow; the criteria move into the query with real data.
+    /// - Parameter filter: the criteria the listings are narrowed and ordered by.
+    /// - Returns: every matching listing.
+    public func listings(
+        matching filter: ListingFilter = .init()
+    ) async throws -> [Listing] {
+        try await ListingRecord.query(on: fluent.db())
+            .with(\.$shop)
+            .all()
+            .map(\.snapshot)
+            .filter(filter.matches)
+            .sorted(by: filter.ordersBefore)
+    }
+
+    /// Fetches the name of every publisher with a listing, in alphabetical order.
+    public func publishers() async throws -> [String] {
+        try await ListingRecord.query(on: fluent.db())
+            .unique()
+            .sort(\.$publisher)
+            .all(\.$publisher)
+    }
+
+    /// Fetches the shop with the given slug.
+    /// - Parameter slug: the shop's URL slug.
+    /// - Returns: the shop, or `nil` when none has the slug.
+    public func shop(
+        slug: String
+    ) async throws -> Shop? {
+        try await ShopRecord.query(on: fluent.db())
+            .filter(\.$slug == slug)
+            .first()?
+            .snapshot
+    }
+
+}