Added the catalogue models and seed to support phase 2 of the POC prototype in the Persistence package.

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

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+import FluentKit
+import HummingbirdFluent
+
+/// Reads and creates accounts through the default database.
+public struct AccountRepository: Sendable {
+
+    // MARK: Constants
+
+    /// The email of the demo buyer the prototype's stubbed passkey signs in.
+    public static let demoEmail = Seed.accounts[0].email
+
+    // 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 account with the given email, creating it when there is none: one step both signs in and joins.
+    ///
+    /// A new account is named after the email's local part until its owner picks a display name.
+    /// - Parameter email: the account's normalized email address.
+    /// - Returns: the account, existing or new.
+    public func account(
+        email: String
+    ) async throws -> User {
+        if let record = try await UserRecord.query(on: fluent.db())
+            .filter(\.$email == email)
+            .first()
+        {
+            return try record.snapshot
+        }
+
+        let record = UserRecord(
+            email: email,
+            displayName: String(email.prefix { $0 != "@" })
+        )
+
+        try await record.save(on: fluent.db())
+
+        return try record.snapshot
+    }
+
+}