Ensure styling in login-forms for multiple authenticators is usable

[brynwhyman]

We could expect some sites to have multiple authenticators (like an optional RealMe login). We should confirm that the styling presented by login-forms is adequate and allows a developer to alter this according to their requirements.

ACs

• With login-forms installed alongside another login module (like RealMe), both login forms are available for use.
• The styling appears professional.

[elliot-sawyer]

I raised a similar issue with Watea a few months ago and created a shim for it. If the theme is bootstrap-based and supports tabs, a similar approach could be taken.

See https://github.com/elliot-sawyer/watea-multiauthenticator-login for implementation

[brynwhyman]

Thanks for noting that @elliot-sawyer, I actually made reference of your work with the team when I raised this issue ;)