Support for HTTP Basic Auth

Hello grist-core team!

I've built a small internal app using grist-core and I really love what you've done with this software. At the moment I am talking with our IT department, and they are not very fond of the idea of running an extra SAML service. Presently all authentication runs through a web server which uses an LDAP backend. Now, I'm no web technology expert, but I believe that is essentially HTTP basic auth. I would like to know which steps would be required to patch grist-core to support this. Any ideas?