H2 Console:
http://localhost:8080/h2-console

JDBC URL: jdbc:h2:file:./data
User Name: sa
Password: password

Почитать:

• Spring Boot CRUD Application with Thymeleaf https://www.baeldung.com/spring-boot-crud-thymeleaf
• Thymeleaf Layout Dialect https://ultraq.github.io/thymeleaf-layout-dialect/
• Tutorial: Using Thymeleaf https://www.thymeleaf.org/doc/tutorials/3.1/usingthymeleaf.html#introducing-thymeleaf
• Working with Cookies in Spring MVC using @CookieValue Annotation https://www.geeksforgeeks.org/working-with-cookies-in-spring-mvc-using-cookievalue-annotation/
• Session Attributes in Spring MVC https://www.baeldung.com/spring-mvc-session-attributes
• LazyInitializationException – What it is and the best way to fix it https://thorben-janssen.com/lazyinitializationexception/