Improve credential redaction handling (#23265)

* redact credentials in config endpoint with sentinel

* backend test

* frontend

* apply widget for credential fields

* i18n

web/src/components/config-form/theme/widgets/PasswordWidget.tsx

@@ -3,8 +3,10 @@ import type { WidgetProps } from "@rjsf/utils";
 import { Input } from "@/components/ui/input";
 import { Button } from "@/components/ui/button";
 import { useState } from "react";
+import { useTranslation } from "react-i18next";
 import { LuEye, LuEyeOff } from "react-icons/lu";
 import { cn } from "@/lib/utils";
+import { REDACTED_CREDENTIAL_SENTINEL } from "@/lib/const";
 import { getSizedFieldClassName } from "../utils";
 
 export function PasswordWidget(props: WidgetProps) {
@@ -21,17 +23,31 @@ export function PasswordWidget(props: WidgetProps) {
     options,
   } = props;
 
+  const { t } = useTranslation(["common"]);
   const [showPassword, setShowPassword] = useState(false);
   const fieldClassName = getSizedFieldClassName(options, "sm");
 
+  // When the backend returns the sentinel, hide it visually and prompt the
+  // user that a value is already saved. The value stays as the sentinel in
+  // form state — backend /config/set strips it so the saved YAML is
+  // preserved when the user doesn't touch the field.
+  const isRedacted = value === REDACTED_CREDENTIAL_SENTINEL;
+  const displayValue = isRedacted ? "" : (value ?? "");
+  const effectivePlaceholder = isRedacted
+    ? t("credentialField.savedPlaceholder", {
+        ns: "common",
+        defaultValue: "Saved — leave blank to keep current",
+      })
+    : placeholder || "";
+
   return (
     <div className={cn("relative", fieldClassName)}>
       <Input
         id={id}
         type={showPassword ? "text" : "password"}
-        value={value ?? ""}
+        value={displayValue}
         disabled={disabled || readonly}
-        placeholder={placeholder || ""}
+        placeholder={effectivePlaceholder}
         onChange={(e) =>
           onChange(e.target.value === "" ? undefined : e.target.value)
         }
@@ -46,7 +62,7 @@ export function PasswordWidget(props: WidgetProps) {
         size="sm"
         className="absolute right-0 top-0 h-full px-3 hover:bg-transparent"
         onClick={() => setShowPassword(!showPassword)}
-        disabled={disabled}
+        disabled={disabled || isRedacted}
       >
         {showPassword ? (
           <LuEyeOff className="h-4 w-4" />