Create Custom Short URLs

[yuktha-c-reddy]

Currently, the URL shortener generates random URLs. It would be a great enhancement to allow users to create custom short URLs instead of relying solely on randomly generated ones.

Acceptance Criteria:

• Users can input a custom short URL.
• The system verifies the uniqueness and validity of the custom URL.
• If valid, the custom short URL is saved and accessible.
• If invalid, users receive an appropriate error message.

I'd love to contribute to this and i believe I can help implement the feature as described in the issue.