ros2 service replier

[amfern]

Implements ROS2 service

[amfern]

This resolves #51

[amfern]

ping @OpusK, hey can you take a look?

[per1234]

Regarding this CI failure:
https://travis-ci.org/github/ROBOTIS-GIT/ros2arduino/builds/751887104#L405

In file included from /home/travis/.arduino15/packages/arduino/hardware/samd/1.8.11/cores/arduino/SafeRingBuffer.h:25:0,
                 from /home/travis/.arduino15/packages/arduino/hardware/samd/1.8.11/cores/arduino/Uart.h:23,
                 from /home/travis/.arduino15/packages/arduino/hardware/samd/1.8.11/variants/mkr1000/variant.h:164,
                 from /home/travis/.arduino15/packages/arduino/hardware/samd/1.8.11/cores/arduino/Arduino.h:48,
                 from sketch/subscriber.ino.cpp:1:
/home/travis/.arduino15/packages/arduino/hardware/samd/1.8.11/cores/arduino/sync.h:28:22: error: expected unqualified-id before 'for'
 #define synchronized for (__Guard __guard; __guard.enter(); )
                      ^
/home/travis/arduino_ide/libraries/ros2arduino/src/ros2/xrcedds/micro_xrce_dds/lib/include/uxr/client/core/session/session.h:97:10: note: in expansion of macro 'synchronized'
     bool synchronized;
          ^~~~~~~~~~~~
/home/travis/.arduino15/packages/arduino/hardware/samd/1.8.11/cores/arduino/sync.h:28:44: error: '__guard' does not name a type; did you mean '__Guard'?
 #define synchronized for (__Guard __guard; __guard.enter(); )
                                            ^
/home/travis/arduino_ide/libraries/ros2arduino/src/ros2/xrcedds/micro_xrce_dds/lib/include/uxr/client/core/session/session.h:97:10: note: in expansion of macro 'synchronized'
     bool synchronized;
          ^~~~~~~~~~~~
/home/travis/.arduino15/packages/arduino/hardware/samd/1.8.11/cores/arduino/sync.h:28:61: error: expected unqualified-id before ')' token
 #define synchronized for (__Guard __guard; __guard.enter(); )
                                                             ^
/home/travis/arduino_ide/libraries/ros2arduino/src/ros2/xrcedds/micro_xrce_dds/lib/include/uxr/client/core/session/session.h:97:10: note: in expansion of macro 'synchronized'
     bool synchronized;
          ^~~~~~~~~~~~
exit status 1

It has been reported here: arduino/ArduinoCore-samd#596
I don't think it is related to the changes made in this pull request in any way. It's simply that the breakage was introduced in the 1.8.11 release of the Arduino SAMD Boards platform on 2020-12-24, which came after the last CI run, but before this PR was submitted. If you compile the ros2arduino code from the master branch with Arduino SAMD Boards 1.8.11 you'll get the same error.

[OpusK]

@amfern Sorry for the late.

Unfortunately, I no longer have administrative rights to this repo...

[amfern]

Thanks for coming back, i learn alot when tinckering with this repo. And i already moved on to micro_ros_arduino