Missing converter from class java.lang.String to interface org.springframework.security.core.GrantedAuthority, this is needed for field authorities on Entry class

The error message you mentioned indicates that there is a missing converter from the `String` class to the `GrantedAuthority` interface. This converter is needed for the `authorities` field in the `Entry` class.

To resolve this issue, you can create a custom converter that converts a `String` to a `GrantedAuthority` object. Here's an example of how you can implement the converter:

import org.springframework.core.convert.converter.Converter;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.SimpleGrantedAuthority;

public class StringToGrantedAuthorityConverter implements Converter<String, GrantedAuthority> {

    @Override
    public GrantedAuthority convert(String source) {
        return new SimpleGrantedAuthority(source);
    }
}

Once you have the converter implemented, you need to register it with Spring's conversion service. You can do this by adding the following configuration to your application:

import org.springframework.context.annotation.Configuration;
import org.springframework.format.FormatterRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    @Override
    public void addFormatters(FormatterRegistry registry) {
        registry.addConverter(new StringToGrantedAuthorityConverter());
    }
}

By registering the converter, Spring will be able to convert `String` values to `GrantedAuthority` objects when needed, resolving the error you encountered.