Digital Library: Allow 'personal users' to DL.

Users with an account and an UM printer should have some basic access to the Digital Library. To this end, and to remain future proof, the online team has made an extension to its API so now feature budgets can be gauge. At the moment it's only checked wether the user has any access to personal projects at all. If so, the interface shows Digital Library functionality. Known issue: Removing the last printer from DF while still logged in leaves the DL access in the Cura interface until logged out or Cura restarted. Additionally, I think the response for a logged in user without any printer from the API is just 'data = empty list' instead of everything set to False and 0 (which should be the case as they're all listed as required fields in their docs ... maybe I'm missing something). In any case, the code as is now can handle that as well.

CURA-8138

plugins/DigitalLibrary/src/DigitalFactoryFeatureBudgetResponse.py

@@ -0,0 +1,43 @@
+# Copyright (c) 2021 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+from .BaseModel import BaseModel
+from typing import Optional
+
+
+class DigitalFactoryFeatureBudgetResponse(BaseModel):
+    """Class representing the capabilities of a user account for Digital Library.
+       NOTE: For each max_..._projects fields, '-1' means unlimited!
+    """
+
+    def __init__(self,
+                 library_can_use_business_value: Optional[bool] = False,
+                 library_can_use_comments: Optional[bool] = False,
+                 library_can_use_status: Optional[bool] = False,
+                 library_can_use_tags: Optional[bool] = False,
+                 library_can_use_technical_requirements: Optional[bool] = False,
+                 library_max_organization_shared_projects: Optional[int] = False,  # -1 means unlimited
+                 library_max_private_projects: Optional[int] = False,  # -1 means unlimited
+                 library_max_team_shared_projects: Optional[int] = False,  # -1 means unlimited
+                 **kwargs) -> None:
+
+        self.library_can_use_business_value = library_can_use_business_value
+        self.library_can_use_comments = library_can_use_comments
+        self.library_can_use_status = library_can_use_status
+        self.library_can_use_tags = library_can_use_tags
+        self.library_can_use_technical_requirements = library_can_use_technical_requirements
+        self.library_max_organization_shared_projects = library_max_organization_shared_projects  # -1 means unlimited
+        self.library_max_private_projects = library_max_private_projects  # -1 means unlimited
+        self.library_max_team_shared_projects = library_max_team_shared_projects  # -1 means unlimited
+        super().__init__(**kwargs)
+
+    def __repr__(self) -> str:
+        return "max private: {}, max org: {}, max team: {}".format(
+            self.library_max_private_projects,
+            self.library_max_organization_shared_projects,
+            self.library_max_team_shared_projects)
+
+    # Validates the model, raising an exception if the model is invalid.
+    def validate(self) -> None:
+        super().validate()
+        # No validation for now, as the response can be "data: []", which should be interpreted as all False and 0's