refactor: reuse oauthVerify function

server/src/auth/oauthVerify.js

@@ -0,0 +1,24 @@
+import User from '../models/user.js'
+
+export default async function oauthVerify(provider, profile, query, cb) {
+  process.nextTick(async () => {
+    const email = profile.emails[0]?.value
+    if (!email) {
+      return cb(new Error('No email found'))
+    }
+
+    let user = await User.findOne(query)
+    if (!user) {
+      user = await User.findOne({ email })
+      if (!user) {
+        const newUser = { email }
+        newUser[provider] = profile
+        return cb(null, { newUser })
+      }
+      user[provider] = profile
+      await user.save()
+    }
+
+    return cb(null, user)
+  })
+}