Add model to represent packages and export information to QML

We'll construct a bunch of these when we receive information from the API.

Contributes to issue CURA-8556.

plugins/Marketplace/PackageList.py

@@ -2,9 +2,14 @@
 # Cura is released under the terms of the LGPLv3 or higher.
 
 from PyQt5.QtCore import Qt
-
+from typing import List, TYPE_CHECKING
 from UM.Qt.ListModel import ListModel
 
+from .PackageModel import PackageModel  # This list is a list of PackageModels.
+
+if TYPE_CHECKING:
+    from PyQt5.QtCore import QObject
+
 class PackageList(ListModel):
     """
     Represents a list of packages to be displayed in the interface.
@@ -13,9 +18,12 @@ class PackageList(ListModel):
     paginated.
     """
 
-    PackageIDRole = Qt.UserRole + 1
+    PackageRole = Qt.UserRole + 1
-    DisplayNameRole = Qt.UserRole + 2
+
-    # TODO: Add more roles here when we need to display more information about packages.
+    def __init__(self, parent: "QObject" = None):
+        super().__init__(parent)
+
+        self._packages: List[PackageModel] = []
 
     def _update(self) -> None:
         # TODO: Get list of packages from Marketplace class.

plugins/Marketplace/PackageModel.py

@@ -0,0 +1,25 @@
+# Copyright (c) 2021 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+from PyQt5.QtCore import pyqtProperty, QObject
+
+class PackageModel(QObject):
+    """
+    Represents a package, containing all the relevant information to be displayed about a package.
+
+    Effectively this behaves like a glorified named tuple, but as a QObject so that its properties can be obtained from
+    QML.
+    """
+
+    def __init__(self, package_id: str, display_name: str, parent: QObject = None):
+        super().__init__(parent)
+        self._package_id = package_id
+        self._display_name = display_name
+
+    @pyqtProperty(str, constant = True)
+    def packageId(self) -> str:
+        return self._package_id
+
+    @pyqtProperty(str, constant = True)
+    def displayName(self) -> str:
+        return self._display_name