Provide --client-id argument to override hard-coded clientid (eg: for soundcloud extractor)

[maxux]

Prerequisites

• I've verified and I assure that I'm running youtube-dl 2017.10.15.1
• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

Issue

Soundcloud extractor returns HTTP 401, after search on existing issues, it looks like CLIENT_ID on the code needs to be updated.

Related Issues: #11327 and #12376

I changed the CLIENT_ID to a client-id I own from soundcloud API and it works again. I guess the client-id hardcoded is expired/revoked/ban.

Feature request

It would be cool to add a --client-id argument to override hardcoded client-id. You can create your own API Client ID via https://soundcloud.com/you/apps and then use this client-id. This could provide an easy-way to bypass 401 when hardcoded client-id is not working anymore.

In addition, it could helps to debug/confirm issue related to client-id without modifying the code. This could not be limited to soundcloud.

[maxux]

@dstftw Hello, I think referring this issue on the commit and not closing it would have been better. This issue is mainly about the feature request, not only about the issue.

[jacksgt]

Thanks for this fix! 👍
(I was on 2017.10.15, fixed in 2017.10.20)