This route authenticates a local user using email and password. Send the
frontegg-vendor-host as a header to declare which vendor. This is your domain name in the Frontegg Portal ➜ Workspace Settings ➜ Domains ➜ Domain Name. Optionally, send login information for the user as POST body params. Include the invitation token if the user is signing up by invitation. Send the recaptcha token if the recaptcha is enabled for login.