feat: set label descriptions in repo_checks

repo_checks currently normalizes label names and colors. With this
commit, it will also normalize the label description.

We add some hopefully-uncontroversial descriptions to the existing list of
labels.

Part of:
https://openedx.atlassian.net/wiki/spaces/COMM/pages/3695214629/openedx+org-wide+labels#2.-Proposal%3A-List-of-starter-labels

migrate/labels.yml

@@ -1,12 +1,22 @@
 # Repository labels to be synced across the entire org.
 # For picking hex colors, you can use: https://www.htmlcolor-picker.com/
+
 - name: ":hammer and wrench: maintenance"
   color: "169509"  # grassy green
+  description: "Work that must be done for platform health"
+
 - name: "waiting on author"
   color: "bfd6f6"  # baby blue
+  description: "PR reviewers are waiting on the author to answer questions, fix tests, etc."
+
 - name: "closed-inactivity"
   color: "dbcd00"  # gold
+  description: "PR was closed because the author abandoned it"
+
 - name: "needs test run"
   color: "f5424b"  # crimson red
+  description: "Author's first PR to a repository, awaiting test authorization from Axim"
+
 - name: "good first issue :tada:"
   color: "42dd35"  # lime green
+  description: "A good task for a newcomer to start with"

migrate/repo_checks.py

@@ -396,6 +396,7 @@ class EnsureLabels(Check):
     # Each item should be a dict with the fields:
     #  name: str
     #  color: str (rrggbb hex string)
+    #  description: str
     labels: list
 
     with open(LABELS_YAML_PATH) as labels_yaml:
@@ -420,7 +421,11 @@ def check(self):
         )
 
         existing_labels = {
-            self._simplify_label(label.name): {"color": label.color, "name": label.name}
+            self._simplify_label(label.name): {
+                "color": label.color,
+                "name": label.name,
+                "description": label.description,
+            }
             for label in labels
         }
         self.missing_labels = []
@@ -429,7 +434,8 @@ def check(self):
         #     {
         #         "current_label": "<current label name>",
         #         "new_label": "<new_label_name>",
-        #         "color": "<new_label_color>",
+        #         "new_color": "<new_label_color>",
+        #         "new_description": "<new_label_description>",
         #     }
         # ]
 
@@ -443,6 +449,7 @@ def check(self):
                             "current_label": existing_labels[simple_name]["name"],
                             "new_label": new_label["name"],
                             "new_color": new_label["color"],
+                            "new_description": new_label["description"],
                         }
                     )
             else:
@@ -486,6 +493,7 @@ def fix(self, dry_run=False):
                         self.repo_name,
                         name=label["current_label"],
                         color=label["new_color"],
+                        description=label["new_description"],
                         new_name=label["new_label"],
                     )
                 except HTTP4xxClientError as e: