Adding Auth Functionality into Kafdrop

[wxin-clio]

Hi, we would like to open a pull request and add authentication functionality into Kafdrop (by adding and configure Spring Security). Just want to touch base with you to see if you like the idea before we open the pull request; otherwise we'll fork the project and host with the auth feature by ourselves. Any suggestions or feedback will be appreciated. Thanks!

[ekoutanov]

@wxinuwaterloo , would you consider doing this work on Kafdrop 3. Your fork might require significant rebasing as the two projects have materially diverged.