Adds delete ssh key method (#260)

* Add delete ssh key method

Author: Costya-Y

maas/client/viscera/sshkeys.py

@@ -41,3 +41,9 @@ class SSHKey(Object, metaclass=SSHKeyType):
     id = ObjectField.Checked("id", check(int), readonly=True)
     key = ObjectField.Checked("key", check(str), readonly=True)
     keysource = ObjectField.Checked("keysource", check_optional(str), readonly=True)
+
+    async def delete(self):
+        """Delete this key."""
+        await self._handler.delete(
+            id=self.id,
+        )

maas/client/viscera/tests/test_sshkeys.py

@@ -48,3 +48,13 @@ def test__sshkey_read(self):
         key_dict = {"id": key_id, "key": make_string_without_spaces(), "keysource": ""}
         SSHKey._handler.read.return_value = key_dict
         self.assertThat(SSHKey.read(id=key_id), Equals(SSHKey(key_dict)))
+
+    def test__sshkey_delete(self):
+        """SSHKeys.read() returns a single SSH key."""
+        SSHKey = make_origin().SSHKey
+        key_id = random.randint(0, 100)
+        ssh_key = SSHKey(
+            {"id": key_id, "key": make_string_without_spaces(), "keysource": ""}
+        )
+        ssh_key.delete()
+        SSHKey._handler.delete.assert_called_once_with(id=key_id)