Why does logging in through oauth always create a new user instead of binding an existing user?

[zhimibuwudn]

Describe the bug

Why does logging in through oauth always create a new user instead of binding an existing user? For example, I want to use the mailbox as an identifier when oauth logs in, if the mailbox exists, how to bind an existing account?

Steps to reproduce

Why does logging in through oauth always create a new user instead of binding an existing user?

The version of Memos you're using

Version: v0.23.0

Screenshots or additional context

No response

[johnnyjoygh]

The current SSO logic is as follows: if the username in the SSO response matches an existing user, the user will be logged in directly; otherwise, a new user will be created. There is no account binding logic.