As previously discussed with Alejandro.

can you please add details to the PR itself? it's not very convenient for anyone (neither me who would first need to check what discussions we had, nor other devs who are not on our matrix channel) to have any details explaining why a PR is useful only in some other place

I made some changes to the signals to make them (in my opinion) more useful, and fixed incorrect documentation.

Please have a look and see if they still do everything you need. This is what I used for testing:

    def init(self):
        super().init()
        self.connect(signals.users.check_signup_email, self._check_signup_email)
        self.connect(signals.users.check_login_data, self._check_login_data)

    def _check_signup_email(self, email, **kwargs):
        print(email, kwargs)
        if email.endswith('@evil.com'):
            return 'YOU SHALL DO NO EVIL'

    def _check_login_data(self, sender, provider, data, **kwargs):
        print(sender, provider, data, kwargs)  # data includes the password as well
        if data['identifier'] == 'moo':
            return 'no cows allowed'

I made some changes to the signals to make them (in my opinion) more useful, and fixed incorrect documentation.

Please have a look and see if they still do everything you need. This is what I used for testing:

    def init(self):
        super().init()
        self.connect(signals.users.check_signup_email, self._check_signup_email)
        self.connect(signals.users.check_login_data, self._check_login_data)

    def _check_signup_email(self, email, **kwargs):
        print(email, kwargs)
        if email.endswith('@evil.com'):
            return 'YOU SHALL DO NO EVIL'

    def _check_login_data(self, sender, provider, data, **kwargs):
        print(sender, provider, data, kwargs)  # data includes the password as well
        if data['identifier'] == 'moo':
            return 'no cows allowed'

TESTED, works for us, thank you.