add possibility to turn off new registrations (#2017)

with LNBITS_ALLOW_NEW_ACCOUNTS=false

while keeping existing users functional (i.e. no allowlist for existing users)

lnbits/helpers.py

@@ -51,6 +51,7 @@ def template_renderer(additional_folders: Optional[List] = None) -> Jinja2Templa
     t.env.globals["LNBITS_THEME_OPTIONS"] = settings.lnbits_theme_options
     t.env.globals["LNBITS_QR_LOGO"] = settings.lnbits_qr_logo
     t.env.globals["LNBITS_VERSION"] = settings.version
+    t.env.globals["LNBITS_NEW_ACCOUNTS_ALLOWED"] = settings.new_accounts_allowed
     t.env.globals["LNBITS_ADMIN_UI"] = settings.lnbits_admin_ui
     t.env.globals["LNBITS_NODE_UI"] = (
         settings.lnbits_node_ui and get_node_class() is not None