Fix login issues

- Properly clear secure token
- Better error messages

lib/api.dart

@@ -471,11 +471,7 @@ class InvenTreeAPI {
 
     if (!response.successful()) {
       debug("Server returned invalid response: ${response.statusCode}");
-      showStatusCodeError(
+      showStatusCodeError(apiUrl, response.statusCode, details: response.data);
-        apiUrl,
-        response.statusCode,
-        details: response.data.toString(),
-      );
       return false;
     }
 
@@ -1535,7 +1531,7 @@ class InvenTreeAPI {
           showStatusCodeError(
             url,
             _response.statusCode,
-            details: response.data.toString(),
+            details: response.data,
           );
         }
       }

lib/user_profile.dart

@@ -112,9 +112,11 @@ class UserProfileDBManager {
       profile.token = secureToken;
     } else if (profile.token.isNotEmpty) {
       // Legacy profile - migrate its plaintext token into secure storage,
-      // and strip it from the Sembast record on next write
+      // and strip it from the Sembast record now. Must use put() (full
+      // replace) rather than update() (merge), otherwise the stale legacy
+      // "token" field survives and gets re-migrated on every future read.
       await _saveToken(key, profile.token);
-      await store.record(key).update(await _db, profile.toJson());
+      await store.record(key).put(await _db, profile.toJson());
     }
 
     return profile;
@@ -185,7 +187,10 @@ class UserProfileDBManager {
       return result;
     }
 
-    await store.record(profile.key).update(await _db, profile.toJson());
+    // put() (full replace) rather than update() (merge) - a legacy record's
+    // stale "token" field must not survive a write, or it will be
+    // re-migrated into secure storage on the next read (see _loadToken)
+    await store.record(profile.key).put(await _db, profile.toJson());
     await _saveToken(profile.key!, profile.token);
 
     return true;

lib/widget/dialogs.dart

@@ -310,19 +310,61 @@ Future<void> showServerError(
 Future<void> showStatusCodeError(
   String url,
   int status, {
-  String details = "",
+  dynamic details,
 }) async {
   String msg = statusCodeToString(status);
   String extra = url + "\n" + "${L10().statusCode}: ${status}";
 
-  if (details.isNotEmpty) {
+  String errorDetails = extractErrorDetails(details);
+
+  if (errorDetails.isNotEmpty) {
     extra += "\n";
-    extra += details;
+    extra += errorDetails;
   }
 
   showServerError(url, msg, extra);
 }
 
+/*
+ * Attempt to extract a human-readable error message from API response data.
+ * The server commonly returns error information under a "detail", "error"
+ * or "errors" key - prefer displaying that over the raw JSON.
+ * Falls back to displaying the raw data as a list of key : value pairs.
+ */
+String extractErrorDetails(dynamic data) {
+  if (data is Map) {
+    for (final key in ["detail", "error", "errors"]) {
+      var value = data[key];
+
+      if (value == null) {
+        continue;
+      }
+
+      if (value is List) {
+        return value.map((e) => e.toString()).join("\n");
+      }
+
+      return value.toString();
+    }
+
+    if (data.isNotEmpty) {
+      return data.entries.map((e) => "${e.key}: ${e.value}").join("\n");
+    }
+
+    return "";
+  }
+
+  if (data is List && data.isNotEmpty) {
+    return data.map((e) => e.toString()).join("\n");
+  }
+
+  if (data is String) {
+    return data;
+  }
+
+  return "";
+}
+
 /*
  * Provide a human-readable descriptor for a particular error code
  */