Erro 500

Oi Aron,

Posta aqui suas classes Usuario e AutenticacaoController

Usuario:

package br.com.challenge.alura.models;

import java.util.Collection;
import java.util.List;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.userdetails.UserDetails;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "Usuarios")
public class Usuario implements UserDetails{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false, unique = true)
    private String login;

    @Column(nullable = false)
    private String senha;

    @ManyToMany
    private List<Role> roles;

    @Override
    public Collection<? extends GrantedAuthority> getAuthorities() {
        return this.roles;
    }

    @Override
    public String getPassword() {
        return this.senha;
    }

    @Override
    public String getUsername() {
        return this.login;
    }

    @Override
    public boolean isAccountNonExpired() {
        return true;
    }

    @Override
    public boolean isAccountNonLocked() {
        return true;
    }

    @Override
    public boolean isCredentialsNonExpired() {
        return true;
    }

    @Override
    public boolean isEnabled() {
        return true;
    }
}

AutenticacaoController

package br.com.challenge.alura.controllers;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import br.com.challenge.alura.config.security.token.TokenAppService;
import br.com.challenge.alura.dto.auth.LoginDto;

@RestController
@RequestMapping("/auth")
public class AutenticacaoController {

    @Autowired
    private AuthenticationManager authManager;

    @Autowired
    private TokenAppService tokenService;

    @PostMapping
    public ResponseEntity<?> autenticar(@RequestBody @Valid LoginDto loginDto) {
        UsernamePasswordAuthenticationToken dadosLogin = loginDto.converter();

        try {
            Authentication authentication = authManager.authenticate(dadosLogin);
            String token = tokenService.gerar(authentication);
            System.out.println(token);

            return ResponseEntity.ok().build();
        } catch (AuthenticationException e) {
            return ResponseEntity.badRequest().build();
        }
    }
}

Certinho. Esqueci de pedir mais uma: TokenAppService

TokenAppService

package br.com.challenge.alura.config.security.token;

import java.util.Date;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Service;

import br.com.challenge.alura.models.Usuario;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

@Service
public class TokenAppService {

    @Value("${forum.jwt.expiration}")
    private String expiration;

    @Value("${forum.jwt.secret}")
    private String secret;


    public String gerar(Authentication authentication) {
        Usuario logado=  (Usuario) authentication.getPrincipal(); 

        return Jwts.builder()
                .setIssuer("API de controle familiar")
                .setSubject(logado.getUsername())
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + Long.parseLong(expiration)))
                .signWith(SignatureAlgorithm.HS256, secret)
                .compact();
    }

}

AutenticacaoService

package br.com.challenge.alura.config.security;
import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;
import br.com.challenge.alura.models.Usuario;
import br.com.challenge.alura.repositories.UsuarioRepository;
import lombok.RequiredArgsConstructor;

@Service
@RequiredArgsConstructor
public class AutenticacaoService implements UserDetailsService {
    private final UsuarioRepository usuarioRepository;

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        Usuario usuario = usuarioRepository.findByLogin(username)
                .orElseThrow(() -> new UsernameNotFoundException("Usuario " + username + " não encontrado!"));
        return new User(usuario.getLogin(), usuario.getPassword(), true, true, true, true, usuario.getAuthorities());
    }
}

O problema é que na sua classe AutenticacaoService você não está retornando um objeto Usuario e sim User:

return new User(usuario.getLogin(), usuario.getPassword(), true, true, true, true, usuario.getAuthorities());

Mas na classe TokenAppService está tentando fazer um cast para Usuario:

Usuario logado=  (Usuario) authentication.getPrincipal(); 

Altere essa linha para:

User logado=  (User) authentication.getPrincipal(); 

Ou utilize a própria classe Usuario mesmo.