feat: init tutorial 4

.gitignore

README.md

abstract-uml.png

build.gradle

gradle/wrapper/gradle-wrapper.jar

gradle/wrapper/gradle-wrapper.properties

gradlew

gradlew.bat

settings.gradle

singleton-uml.png

...a/id/ac/ui/cs/advprog/tutorial4/Tutorial4Application.java

...4/authentication/controller/AuthenticationController.java

...4/authentication/controller/AuthorizedPageController.java

...hentication/controller/advice/GlobalExceptionHandler.java

...g/tutorial4/authentication/core/AuthentiationManager.java

.../ac/ui/cs/advprog/tutorial4/authentication/core/Util.java

...4/authentication/exceptions/InvalidPasswordException.java

...ial4/authentication/exceptions/InvalidTokenException.java

...entication/exceptions/UsernameAlreadyExistsException.java

...l4/authentication/exceptions/UsernameAlreadyLoggedIn.java