Always subscribe to packages after installing them

Now that we subscribe for all situations where a package is installed,
it makes sense to watch package installs and create a 1:1 relation that
way. Prevents code duplication.

CURA-7099

plugins/Toolbox/src/CloudSync/CloudPackageManager.py

@@ -1,23 +1,53 @@
+from UM.Logger import Logger
+from UM.TaskManagement.HttpRequestManager import HttpRequestManager
+from cura.API import Account
 from cura.CuraApplication import CuraApplication
 from ..CloudApiModel import CloudApiModel
 from ..UltimakerCloudScope import UltimakerCloudScope
 
 
-## Manages Cloud subscriptions. When a package is added to a user's account, the user is 'subscribed' to that package
-# Whenever the user logs in on another instance of Cura, these subscriptions can be used to sync the user's plugins
 class CloudPackageManager:
+    """Manages Cloud subscriptions
+
+    When a package is added to a user's account, the user is 'subscribed' to that package.
+    Whenever the user logs in on another instance of Cura, these subscriptions can be used to sync the user's plugins
+
+    Singleton: use CloudPackageManager.getInstance() instead of CloudPackageManager()
+    """
+
+    __instance = None
+
+    @classmethod
+    def getInstance(cls, app: CuraApplication):
+        if not cls.__instance:
+            cls.__instance = CloudPackageManager(app)
+        return cls.__instance
+
     def __init__(self, app: CuraApplication) -> None:
-        self._request_manager = app.getHttpRequestManager()
-        self._scope = UltimakerCloudScope(app)
+        if self.__instance is not None:
+            raise Exception("This is a Singleton. use getInstance()")
+
+        self._request_manager = app.getHttpRequestManager()  # type: HttpRequestManager
+        self.account = app.getCuraAPI().account  # type: Account
+        self._scope = UltimakerCloudScope(app)  # type: UltimakerCloudScope
+
+        app.getPackageManager().packageInstalled.connect(self._onPackageInstalled)
+
+    def unsubscribe(self, package_id: str) -> None:
+        url = CloudApiModel.userPackageUrl(package_id)
+        self._request_manager.delete(url=url, scope=self._scope)
 
     def subscribe(self, package_id: str) -> None:
+        """You probably don't want to use this directly. All installed packages will be automatically subscribed."""
+
+        Logger.debug("Subscribing to {}", package_id)
         data = "{\"data\": {\"package_id\": \"%s\", \"sdk_version\": \"%s\"}}" % (package_id, CloudApiModel.sdk_version)
         self._request_manager.put(url=CloudApiModel.api_url_user_packages,
                                   data=data.encode(),
                                   scope=self._scope
                                   )
 
-    def unsubscribe(self, package_id: str) -> None:
-        url = CloudApiModel.userPackageUrl(package_id)
-        self._request_manager.delete(url=url, scope=self._scope)
-
+    def _onPackageInstalled(self, package_id: str):
+        if self.account.isLoggedIn:
+            # We might already be subscribed, but checking would take one extra request. Instead, simply subscribe
+            self.subscribe(package_id)