piket-cli: Allow setting Aardbei options via environment

piket_client/cli.py

@@ -220,8 +220,8 @@ def print_error(msg: str) -> None:
 
 
 @cli.group()
-@click.option("--token", required=True)
-@click.option("--endpoint", default="http://localhost:3000")
+@click.option("--token", required=True, envvar="AARDBEI_TOKEN")
+@click.option("--endpoint", default="http://localhost:3000", envvar="AARDBEI_ENDPOINT")
 @click.pass_context
 def aardbei(ctx, token: str, endpoint: str) -> None:
     ctx.ensure_object(dict)