refactor_AuthenticationEndpoint

[casalsgh]

Removed explicit type declarations for private properties: Since TypeScript can infer the types based on the assigned values, there's no need to explicitly specify the types for embeddedLoginSuccessMessage and embeddedLoginFailureMessage. The types will be inferred as string automatically.

Renamed persis parameter to persist: The parameter name persis was a typo and didn't match the actual parameter name used in the code (persist). I corrected the parameter name to match the usage in the method.

Extracted common logic to a separate method: I created a new private method called getAppSetting to handle the retrieval of app settings. This method takes the read accessor and the settingId as parameters, and it returns the value of the specified app setting. This extraction improves code readability and eliminates code duplication.