Gem::GemcutterUtilities#sign_in

# File tmp/rubies/ruby-4.1.0-preview1/lib/rubygems/gemcutter_utilities.rb, line 168
def sign_in(sign_in_host = nil, scope: nil)
  sign_in_host ||= host
  pretty_host = pretty_host(sign_in_host)
  # Stopping because the store cannot be read would close the one command
  # that can re-authenticate. A flag rather than an argument keeps #api_key
  # callable with no arguments, as command plugins that override it define it.
  @recognizing_session = true
  signed_in = begin
    api_key
  ensure
    @recognizing_session = false
  end

  if signed_in
    say "You are already signed in on #{pretty_host}."
    return
  end
  say "Enter your #{pretty_host} credentials."
  say "Don't have an account yet? " \
      "Create one at #{sign_in_host}/sign_up"

  identifier = ask "Username/email: "
  password   = ask_for_password "      Password: "
  say "\n"

  key_name     = get_key_name(scope)
  scope_params = get_scope_params(scope)
  profile      = get_user_profile(identifier, password)
  mfa_params   = get_mfa_params(profile)
  all_params   = scope_params.merge(mfa_params)
  warning      = profile["warning"]
  credentials  = { identifier: identifier, password: password }

  say "#{warning}\n" if warning

  response = rubygems_api_request(:post, "api/v1/api_key",
                                  sign_in_host, credentials: credentials, scope: scope) do |request|
    request.basic_auth identifier, password
    request.body = Gem::URI.encode_www_form({ name: key_name }.merge(all_params))
  end

  with_response response do |resp|
    say "Signed in with API key: #{key_name}."
    set_api_key host, resp.body
  end
end