LocalizationService.ImportResourcesFromXml() allows inserting duplicate resources

[alinmircea]

nopCommerce version: 4.30 and probably lower

Steps to reproduce the problem:

1. Use LocalizationService.ImportResourcesFromXml() to import duplicate resources.

2. Afterwards try to query the LocaleStringResource repository and cas toDictionary as ImportResourcesFromXml is doing :

var lsNamesList = _lsrRepository.Table.Where(lsr => lsr.LanguageId == language.Id).ToDictionary(lsr => lsr.ResourceName, lsr => lsr);

Error will be received on the ToDictionary cast: "An item with the same key has already been added. Key: Admin.Configuration.Languages.Fields.FlagImage"

ImportResourcesFromXml should not allow duplicate inserts based on resource key.