docs: private void saveTrustedHost( String fingerprint ) throws IOException
      {
          this.fingerprint = fingerprint;
  
          logger.info( "Adding %s as known and trusted certificate for %s.", fingerprint, serverId );
          createKnownCertFileIfNotExists();
  
          assertKnownHostFileWritable();
          try ( BufferedWriter writer = new BufferedWriter( new FileWriter( knownHosts, true ) ) )
          {
              writer.write( serverId + " " + this.fingerprint );
              writer.newLine();
          }
      }