Authentication error messages from PAS Plugins aren't returned by the restapi

[djay]

All errors result in the same generic error message which can be misleading

plone.restapi/src/plone/restapi/services/auth/login.py

Line 64 in b93e410

return dict(

The method used by most PAS Plugins is the status message. Either for information purposes or errors about why the login was not successful. The status messages should be passed via the api so the client can display them

An example of a plugin is

https://github.com/collective/Products.LoginLockout/blob/506ff80b8066e0c26acc3e9cb7c05a76e4b96787/Products/LoginLockout/plugin.py#L232

[djay]

The message is passed as a cookie but this might not be the preferred method. Either Volto needs to read the cookies or the restapi should convert the cookies to header or json response.