title: Installing private package from Github Package registry fails with not found/not authorized
body: <p>I created and published a private Github package. Trying to install it with yarn at first, I face the following issue:</p>
  
  <p>Whether I try with yarn or npm, it cannot find the package at all although following the exact steps documented by Github (<a href="https://help.github.com/en/github/managing-packages-with-github-package-registry/configuring-npm-for-use-with-github-package-registry" rel="noreferrer">https://help.github.com/en/github/managing-packages-with-github-package-registry/configuring-npm-for-use-with-github-package-registry</a>).</p>
  
  <p>My <code>.yarnrc</code>:</p>
  
  <p><code>registry "https://npm.pkg.github.com/OWNER"</code></p>
  
  <p>With yarn, it continuously tries to look for the package at <code>https://registry.yarnpkg.com/@GITHUB_USERNAME</code> instead of the registry I entered above.</p>
  
  <p><em>Remark: in <code>.yarnrc</code> registries need to be added following a slightly different syntax:</em></p>
  
  <p><code>registry "https://npm.pkg.github.com/"</code></p>
  
  <p>So far I started to also play around with a mix of <code>.npmrc</code> and <code>.yarnrc</code> configurations but no luck.</p>
  
  <p>-</p>
  
  <p><strong>EDIT (Partly solved)</strong></p>
  
  <p>I figured out how to actually access the package, both using npm or - in my case - yarn. Now I face the issue of a <code>Request failed \"401 Unauthorized\"</code> error, although I added the credentials on top of <code>.yarnrc</code>:</p>
  
  <p><code>//npm.pkg.github.com/:_authToken=AUTH_TOKEN</code></p>
  
  <p>Doing the same in <code>.npmrc</code> doesn't work either.</p>