web ui: New setting for browser-based login

This is useful in cases where OIDC login is active
which would then redirect the user to a central
login page.

See https://github.com/Kozea/Radicale/issues/2143

radicale/web/internal.py

@@ -34,7 +34,27 @@ FALLBACK_MIMETYPE = httputils.FALLBACK_MIMETYPE  # deprecated
 
 class Web(web.BaseWeb):
 
-    def get(self, environ: types.WSGIEnviron, base_prefix: str, path: str,
-            user: str, request_info: dict) -> types.WSGIResponse:
-        return httputils.serve_resource("radicale.web", "internal_data",
-                                        base_prefix, path)
+    def get(
+        self,
+        environ: types.WSGIEnviron,
+        base_prefix: str,
+        path: str,
+        user: str,
+        request_info: dict,
+    ) -> types.WSGIResponse:
+        if path == "/.web/js/config.js":
+            prefer_browser_login = (
+                "true"
+                if self.configuration.get("web", "prefer_browser_login")
+                else "false"
+            )
+            content = (
+                f"export const PREFER_BROWSER_LOGIN = {prefer_browser_login};\n".encode(
+                    "utf-8"
+                )
+            )
+            headers = {"Content-Type": "application/javascript"}
+            return 200, headers, content, None
+        return httputils.serve_resource(
+            "radicale.web", "internal_data", base_prefix, path
+        )