Check if username is taken

The developer wants to check if a username is taken by comparing it with the usernames in a usersCollection. They are wondering if granting access to all usersCollection documents is necessary in order to construct a list of usernames for comparison. They are also asking if this can be solved with a cloud function. Solution: One possible solution is to use a cloud function to perform the check. Instead of granting access to all usersCollection documents, you can write a cloud function that queries the usersCollection and returns a list of usernames. Then, you can compare the inputted username with this list in the cloud function itself and return the result. This way,