i want to use azure ad b2c to manage authentication. i searched the internet and find the documents here: https://docs.microsoft.com/en-us/azure/app-service/configure-authentication-provider-aad?toc=/azure/azure-functions/toc.json
but i still do not know how i can use azure ad b2c in my azure functions. For example how can i get the email address of the logined user who send request to the azure function? Thank you!