address review comments

- more inline documentation
 - don't explicitly specify audience
 - approver is optional in `generate_key`
 - ADD -> RUN for better caching of jwtproxy

util/generatepresharedkey.py

@@ -6,7 +6,7 @@ from timeparse import ParseDatetime
 
 import argparse
 
-def generate_key(approver, service, name, expiration_date=None, notes=None):
+def generate_key(service, name, approver=None, expiration_date=None, notes=None):
   metadata = {
     'created_by': 'CLI tool',
   }