[Feedback] Conan Essentials - `user/channel` advice

The course strongly encourages using custom user/channel for packages that were _built_ locally, not from Conan Center.
I agree for proprietary recipes or recipes that were written/created out of the CCI so maybe I just misunderstood the advice here.

The issue with the advice is that a new user may think that migrating CCI recipes to `company/stable` scheme is the way to go for vendoring recipes to a private remote. Which is practically a bad user experience since Conan provides very poor overriding capabilities in its interfaces and the only way to prevent "leaking" of packages through a private remote would be to override _all_ requirements in vendored recipes, which is a poor application of one's effort and time.

My personal advice is to actually _preserve_ the original `user/channel` if you intent to use the binaries as-if or in-place of CCI created binaries and control the binary origin through the remote list only.

Review the Conan Essentials course guidance on custom user/channel values for locally built packages. Compare the current advice with the issue's recommendation to preserve the original user/channel for vendored Conan Center packages and control binary origin through remotes; done means the guidance clearly distinguishes these cases.

Written by the indexing model from the issue text.