feat: add auth operations to facade

api/src/main/java/cz/muni/fi/pa165/icehockeymanager/dto/UserDto.java

+package cz.muni.fi.pa165.icehockeymanager.dto;
+
+import cz.muni.fi.pa165.icehockeymanager.security.Roles;
+import lombok.Getter;
+import lombok.Setter;
+
+import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.NotNull;
+import java.util.Objects;
+
+@Getter @Setter
+public final class UserDto {
+
+    @NotNull
+    private Long id;
+
+    @NotBlank
+    private Long username;
+
+    @NotNull
+    private Roles role;
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof UserDto)) return false;
+        UserDto userDto = (UserDto) o;
+        return Objects.equals(getUsername(), userDto.getUsername());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(getUsername());
+    }
+}

api/src/main/java/cz/muni/fi/pa165/icehockeymanager/facades/UserAuthFacade.java

 package cz.muni.fi.pa165.icehockeymanager.facades;
 
+import cz.muni.fi.pa165.icehockeymanager.dto.UserDto;
+import cz.muni.fi.pa165.icehockeymanager.exceptions.UsernameTakenException;
+
+import java.util.Optional;
+
 /**
  * Facade facilitating user authentication
  * and authorization.
  */
 public interface UserAuthFacade {
+    /**
+     * Authenticate user
+     * @param username username
+     * @param password plaintext password
+     * @return true if the password is correct, else false
+     */
+    Optional<UserDto> authenticateUser(String username, String password);
+
+    /**
+     * Create new League Manager account
+     * @param username username
+     * @param password plaintext password
+     * @return User if exists
+     *
+     * @throws UsernameTakenException if username is already taken by another user
+     */
+    UserDto createLeagueManager(String username, String password);
+
+    /**
+     * Create new Team Manager account
+     * @param username username
+     * @param password plaintext password
+     * @return User if exists
+     *
+     * @throws UsernameTakenException if username is already taken by another user
+     */
+    UserDto createTeamManager(String username, String password);
 }

service/src/main/java/cz/muni/fi/pa165/icehockeymanager/facades/UserAuthFacadeImpl.java

 package cz.muni.fi.pa165.icehockeymanager.facades;
 
+import cz.muni.fi.pa165.icehockeymanager.dto.UserDto;
+
+import java.util.Optional;
+
 public class UserAuthFacadeImpl implements UserAuthFacade {
+    @Override
+    public Optional<UserDto> authenticateUser(String username, String password) {
+        return Optional.empty();
+    }
+
+    @Override
+    public UserDto createLeagueManager(String username, String password) {
+        return null;
+    }
+
+    @Override
+    public UserDto createTeamManager(String username, String password) {
+        return null;
+    }
 }