Brought longview-related functionality to API parity (#257)

## 📝 Description

Brought longview-related functionality to API parity

## ✔️ How to Test

`pytest test`

Ticket: TPT-1889

Author: ezilber-akamai-zz

linode_api4/groups/longview.py

@@ -1,6 +1,10 @@
 from linode_api4.errors import UnexpectedResponseError
 from linode_api4.groups import Group
-from linode_api4.objects import LongviewClient, LongviewSubscription
+from linode_api4.objects import (
+    LongviewClient,
+    LongviewPlan,
+    LongviewSubscription,
+)
 
 
 class LongviewGroup(Group):
@@ -60,3 +64,40 @@ def subscriptions(self, *filters):
         :rtype: PaginatedList of LongviewSubscription
         """
         return self.client._get_and_filter(LongviewSubscription, *filters)
+
+    def longview_plan_update(self, longview_subscription):
+        """
+        Update your Longview plan to that of the given subcription ID.
+
+        :param longview_subscription: The subscription ID for a particular Longview plan.
+                                      A value of null corresponds to Longview Free.
+        :type longview_subscription: str
+
+        :returns: The updated Longview Plan
+        :rtype: LongviewPlan
+        """
+
+        if longview_subscription not in [
+            "",
+            "longview-3",
+            "longview-10",
+            "longview-40",
+            "longview-100",
+        ]:
+            raise ValueError(
+                "Invalid longview plan subscription: {}".format(
+                    longview_subscription
+                )
+            )
+
+        params = {"longview_subscription": longview_subscription}
+
+        result = self.client.post(
+            LongviewPlan.api_endpoint, model=self, data=params
+        )
+
+        plan = LongviewPlan(self.client, result["id"], result)
+
+        plan.invalidate()
+
+        return plan

linode_api4/objects/longview.py

@@ -36,3 +36,20 @@ class LongviewSubscription(Base):
         "clients_included": Property(),
         "price": Property(),
     }
+
+
+class LongviewPlan(Base):
+    """
+    The current Longview Plan an account is using.
+
+    API Documentation: https://www.linode.com/docs/api/longview/#longview-plan-view
+    """
+
+    api_endpoint = "/longview/plan"
+
+    properties = {
+        "id": Property(identifier=True),
+        "label": Property(),
+        "clients_included": Property(),
+        "price": Property(),
+    }

test/fixtures/longview_plan.json

@@ -0,0 +1,9 @@
+{
+    "clients_included": 10,
+    "id": "longview-10",
+    "label": "Longview Pro 10 pack",
+    "price": {
+      "hourly": 0.06,
+      "monthly": 40
+    }
+}

test/linode_client_test.py

@@ -502,6 +502,21 @@ def test_client_create_with_label(self):
             self.assertEqual(m.call_url, "/longview/clients")
             self.assertEqual(m.call_data, {"label": "test_client_1"})
 
+    def test_update_plan(self):
+        """
+        Tests that you can submit a correct longview plan update api request
+        """
+        with self.mock_post("/longview/plan") as m:
+            result = self.client.longview.longview_plan_update("longview-100")
+            self.assertEqual(m.call_url, "/longview/plan")
+            self.assertEqual(
+                m.call_data["longview_subscription"], "longview-100"
+            )
+            self.assertEqual(result.id, "longview-10")
+            self.assertEqual(result.clients_included, 10)
+            self.assertEqual(result.label, "Longview Pro 10 pack")
+            self.assertIsNotNone(result.price)
+
     def test_get_subscriptions(self):
         """
         Tests that Longview subscriptions can be retrieved

test/objects/longview_test.py

@@ -1,10 +1,31 @@
 from datetime import datetime
 from test.base import ClientBaseCase
 
-from linode_api4.objects import LongviewClient, LongviewSubscription
+from linode_api4.objects import (
+    LongviewClient,
+    LongviewPlan,
+    LongviewSubscription,
+)
 from linode_api4.objects.base import MappedObject
 
 
+class LongviewPlanTest(ClientBaseCase):
+    """
+    Tests methods of the LongviewPlan class
+    """
+
+    def test_get_plan(self):
+        """
+        Tests that a plan is loaded correctly
+        """
+        plan = LongviewPlan(self.client, "longview-10")
+
+        self.assertEqual(plan.id, "longview-10")
+        self.assertEqual(plan.clients_included, 10)
+        self.assertEqual(plan.label, "Longview Pro 10 pack")
+        self.assertIsNotNone(plan.price)
+
+
 class LongviewClientTest(ClientBaseCase):
     """
     Tests methods of the LongviewClient class