add missing metadata and assignment methods in describegroups
add missing metadata and assignment methods in describegroups

mailgun/sarama,Shopify/sarama,vrischmann/sarama,VividCortex/sarama,DataDog/sarama,mailgun/sarama,VividCortex/sarama,raisemarketplace/sarama,vrischmann/sarama,Shopify/sarama,remerge/sarama,remerge/sarama,DataDog/sarama,raisemarketplace/sarama