0.16.2

• added new tandoor Theme and made it the default for new accounts
• added prometheus metrics to monitor instance
• added caching support for signed s3 urls
• changed url of invite links (old route will work for a few more updates)
• changed streamlined the signup process and cleaned up inconsistencies
• removed support for username specification in invite links (cool feature but makes the signup code messy and custom which is never good for auth related code)
• fixed importer would always import all keywords #645
• fixed removing book entries was broken #660
• fixed importer failing when description is too long #651
• fixed issue when merging units/ingredients #648
• fixed url import sometimes failed on image import #694