OSF: Used model.NewPointer everywhere (#27838)

```release-note
NONE
```

server/channels/app/oauth.go

@@ -627,7 +627,7 @@ func (a *App) LoginByOAuth(c request.CTX, service string, userData io.Reader, te
 			map[string]any{"Service": service}, "", http.StatusBadRequest)
 	}
 
-	user, err := a.GetUserByAuth(model.NewString(*authUser.AuthData), service)
+	user, err := a.GetUserByAuth(model.NewPointer(*authUser.AuthData), service)
 	if err != nil {
 		if err.Id == MissingAuthAccountError {
 			user, err = a.CreateOAuthUser(c, service, bytes.NewReader(buf.Bytes()), teamID, tokenUser)