fix: Raise error if waved cannot find public/private dir #2130

[92ammarraza]

The PR fulfills these requirements: (check all the apply)

• It's submitted to the main branch.
• When resolving a specific issue, it's referenced in the PR's title (e.g. feat: Add a button #xxx, where "xxx" is the issue number).
• When resolving a specific issue, the PR description includes Closes #xxx, where "xxx" is the issue number.
• If changes were made to ui folder, unit tests (make test) still pass.
• New/updated tests are included

Related issue #2130

Overview:
This pull request addresses the issue #2130 , where waved would start without error even if the specified public/private directories were missing or incorrectly configured. The changes introduce error checking during server startup to ensure these directories exist and are accessible.

Changes:

• Added a checkDirectory function in server.go to validate the existence of public and private directories.
• Integrated directory checks during the server initialization phase.
• Server now fails to start with a clear error message if either directory is missing or inaccessible.

Testing

• Tested server startup with current directory paths, an error message is seen on the terminal.

Closes #2130

[mturoci]

Thanks @92ammarraza! A small refactor needed and should be good to go.

[mturoci]

Hey @92ammarraza. Make sure the comments are addressed in the correct branch. File changes view doesn't show your latest changes.

[92ammarraza]

Hey @mturoci , Me and @johnmrzo are working together in team on this for a class. He has pushed the latest changes. Looking forward to your feedback.

[mturoci]

Please make sure you test your code and it works correctly. It does not at the moment. An err is thrown even for valid directories.