Ensure Debian uploads can reference a suite

While reading the code, I found that upload to Debian using the suite was not working.

Feature flagged

The Debian package feature is still behind a feature flag and not yet enabled on GitLab.com.

See #337288.

Testing

• install dput-ng (prerequisite: a Debian or derived distribution - like Ubuntu)

  apt install dput-ng

• Get a private token $api_token (with API scope)

• Create a project, get the $project id

• Define a distribution $codename (for example foobar)

• Create a distribution:

  curl --request POST --header "PRIVATE-TOKEN: $api_token" "http://localhost:3000/api/v4/projects/$project_id/debian_distributions?codename=$codename&suite=unstable"

• Configure dput-ng:

  $ cat <<EOF > dput.cf
  [gitlab]
  method = http
  fqdn = root:$api_token@localhost:3000
  incoming = /api/v4/projects/$project_id/packages/debian
  EOF

• Upload (this package is targeting unstable):

  dput --config=dput.cf --unchecked --no-upload-log gitlab spec/fixtures/packages/debian/sample_1.2.3~alpha2_amd64.changes

• Verify that the package is visible in the interface and available in the repository

  $ sudo mkdir -p /usr/local/share/keyrings
  $ curl --header "PRIVATE-TOKEN: $api_token" \
      "http://localhost:3000/api/v4/projects/$project_id/debian_distributions/$codename/key.asc" \
      | \
      gpg --dearmor \
      | \
      sudo tee /usr/local/share/keyrings/$codename-archive-keyring.gpg \
      > /dev/null
  $ echo "deb [ signed-by=/usr/local/share/keyrings/$codename-archive-keyring.gpg ] http://localhost:3000/api/v4/projects/$project_id/packages/debian $codename main" \
   | sudo tee /etc/apt/sources.list.d/gitlab_project.list > /dev/null
  $ sudo apt-get update
  $ apt show sample-dev