docs: @Nonnull
    public CSP2SourceList addScheme (@Nonnull @Nonempty final String sScheme)
    {
      ValueEnforcer.notEmpty (sScheme, "Scheme");
      ValueEnforcer.isTrue (sScheme.length () > 1 && sScheme.endsWith (":"),
                            () -> "Passed scheme '" + sScheme + "' is invalid!");
      m_aList.add (sScheme);
      return this;
    }