LinkedIn Username Validation

[venkatesh2100]

• Add username support for LinkedIn #92

The validator:
Requests the public profile URL: https://www.linkedin.com/in/{username}/
Does not follow redirects to avoid triggering additional anti-bot checks
Common block responses include status 999, 403, and 429

• Error handling

Result.error("blocked (linkedin)") is returned intentionally when LinkedIn blocks or rate-limits the request.

[kaifcodec]

@venkatesh2100 Thanks for the PR, it looks clean and well structured. However, when I tested it locally, it always returned a 999 status code, which is expected behavior from LinkedIn servers. LinkedIn requires a CSRF token in the request headers, and as a CLI tool it’s tricky to dynamically fetch that token and correctly craft the required headers. Because of this, the current approach won’t work reliably for us.

If we’re able to discover an undocumented or private API that LinkedIn uses for username availability checks, then this could be made to work. If you’re interested in exploring that (it’s a little advanced task), feel free to keep the PR open and push further commits if you find a solution.

Otherwise, you’re welcome to pick up any of the good first issues to work on in the meantime.