Little reactive service to make URLs tiny

• URL shortener
• Redirection
• URL validation -> URL storing
  Didn't use Spring Data repositories because this app needs only two operations - put key-value and get by key. Spring repos are too complex for this use.

• Java 17 - lang
• Gradle - build system
• Redis - database
• Spring WebFlux - reactive library, DI & IoC
• Spring Data Redis (Reactive) - reactive data access
• Apache Commons Lang - string generation
• Apache Commons Validator - URL validation (java.net validator is bad)