ngclient UpdaterConfig: Add docstring

Docstrings for each class are required by linting tool.

Signed-off-by: Martin Vrachev <mvrachev@vmware.com>

tuf/ngclient/config.py

@@ -9,14 +9,27 @@
 
 @dataclass
 class UpdaterConfig:
+    """Used to store Updater configuration.
+
+    Arguments:
+        max_root_rotations: The maximum number of root rotations.
+        max_delegations: The maximum number of delegations.
+        root_max_length: The maxmimum length of a root metadata file.
+        timestamp_max_length: The maximum length of a timestamp metadata file.
+        snapshot_max_length: The maximum length of a snapshot metadata file.
+        targets_max_length: The maximum length of a targets metadata file.
+        prefix_targets_with_hash: When consistent snapshots are used
+            (see https://theupdateframework.github.io/specification/latest/#consistent-snapshots), #pylint: disable=line-too-long
+            target download URLs are formed by prefixing the filename with a
+            hash digest of file content by default. This can be overridden by
+            setting prefix_targets_with_hash to False.
+
+    """
+
     max_root_rotations: int = 32
     max_delegations: int = 32
     root_max_length: int = 512000  # bytes
     timestamp_max_length: int = 16384  # bytes
     snapshot_max_length: int = 2000000  # bytes
     targets_max_length: int = 5000000  # bytes
-    # We need this variable because there are use cases like Warehouse where
-    # you could use consistent_snapshot, but without adding a hash prefix.
-    # By default, prefix_targets_with_hash is set to true to use uniquely
-    # identifiable targets file names for repositories.
     prefix_targets_with_hash: bool = True