Publish diagnostics

[LoyVanBeek]

We can use the diagnostics to check if the Jetson board that runs OpenPose is performing OK or is even connected at all.

[LoyVanBeek]

Because openpose_ros is only called as a service and does not actively publish on a topic, we'll tick diagnostic_updater in it's main service call.

[LoyVanBeek]

For inspiration & reference, take a look at

• jackal_diagnostic_updater.cpp
• jackal_diagnostic_updater.h
• jackal_base.cpp
• diagnostic_updater
• Diagnostic updater example

In Jackal_base, there is a subscription to a status topic, the message of which is stored in the statusCallback. When the diagnostic_updater updates, it triggers all the callbacks added in the constructor. Each such callback does some checking and expands the DiagnosticStatus via a DiagnosticStatusWrapper, eg. like

stat.summary(diagnostic_msgs::DiagnosticStatus::OK, "I'm OK");