Imagine a user logged into my iOS app using their Google account. Months later, they are trying to create an account using their email address (the same one connected to their previous Google social login). Should I
a) serve them an error message reading "This email is tied to a Google-authenticated account already in our system."
b) simply let them create the account again - and figure out how to merge the 2 accounts together seamlessly?
If it's b), can you explain the technical hurdles I'll run into by merging the two accounts? I'm preparing my specs and want to communicate my needs to the engineers as succinctly as possible. Thanks!