message: CHANGE: Let real panda URDF also take arm_id as optional argument
diff: <?xml version='1.0' encoding='utf-8'?>
  <robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="panda">
  + <xacro:arg name="arm_id" default="panda" /> <!-- Name of this panda -->
  <xacro:arg name="hand" default="false" /> <!-- Should a franka_gripper be mounted at the flange?" -->
  <xacro:arg name="gazebo" default="false" /> <!-- Is the robot being simulated in gazebo?" -->
  + <xacro:property name="arm_id" value="$(arg arm_id)" />
  +
  <xacro:unless value="$(arg gazebo)">
  <!-- Create a URDF for a real hardware -->
  <xacro:include filename="$(find franka_description)/robots/panda_arm.xacro" />
  - <xacro:panda_arm safety_distance="0.03"/>
  + <xacro:panda_arm arm_id="${arm_id}" safety_distance="0.03"/>
  <xacro:if value="$(arg hand)">
  <xacro:include filename="$(find franka_description)/robots/hand.xacro"/>
  - <xacro:hand ns="panda" rpy="0 0 ${-pi/4}" connected_to="panda_link8" safety_distance="0.03"/>
  + <xacro:hand ns="${arm_id}" rpy="0 0 ${-pi/4}" connected_to="${arm_id}_link8" safety_distance="0.03"/>
  </xacro:if>
  </xacro:unless>
  <xacro:include filename="$(find franka_description)/robots/utils.xacro" />
  <xacro:include filename="$(find franka_description)/robots/panda_gazebo.xacro" />
  - <xacro:property name="arm_id" value="panda" />
  <xacro:panda_arm arm_id="${arm_id}" />
  <xacro:if value="$(arg hand)">
  