Is it possible to create a new client using a 3rd party form and doing a POST of the company name, contact name, email, timezone, and country? The only authentication possible is basic HTTP username/password.
You will need to use the API to do this, as is described in the Clients API documentation. Authentication is done using an API key via basic auth.
And which script do I post to? Sorry but I'm new to this but starting to figure it out.