Add simple account model for testing login screen

Shared/Account/AccountModel.swift

@@ -0,0 +1,49 @@
+import Foundation
+
+enum AccountError: Error {
+    case invalidCredentials
+    case serverNotFound
+}
+
+struct AccountModel {
+    private(set) var id: UUID?
+    var username: String?
+    var password: String?
+    var server: String?
+
+    mutating func login(
+        to server: String,
+        as username: String,
+        password: String,
+        completion: @escaping (Result<UUID, AccountError>) -> Void
+    ) {
+        let result: Result<UUID, AccountError>
+
+        if server != validServer {
+            result = .failure(.serverNotFound)
+        } else if username == validCredentials["username"] && password == validCredentials["password"] {
+            self.id = UUID()
+            self.username = username
+            self.password = password
+            self.server = server
+            result = .success(self.id!)
+        } else {
+            result = .failure(.invalidCredentials)
+        }
+
+        #if DEBUG
+        // Delay to simulate async network call
+        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+            completion(result)
+        }
+        #endif
+    }
+}
+
+#if DEBUG
+let validCredentials = [
+    "username": "name@example.com",
+    "password": "12345"
+]
+let validServer = "https://test.server.url"
+#endif