add: get clients, servers info

[leeminju531]

Add get clients, servers info

Refer to ros2/ros2cli#916

[leeminju531]

ref
rmw
rmw_implementation
rmw_fastrtps
rmw_cyclonedds
rmw_connextdds

[fujitatomoya]

I think in rmw service endpoints are handled as topics internally, precisely client is DataReader and server is DataWriter to fill in the topic endpoint information. so all the field of rmw_topic_endpoint_info_t can be filled in with calling the graph cache.

IMO i think in rmw we can use rmw_topic_endpoint_info_t as it is now, but i would add comment that says this structure is used for service client and server as well.

[sloretz]

@wjwwood Mind taking a look at this new rmw API 🧇 ?

[methylDragon]

@leeminju531 , any updates from your end?

[leeminju531]

@methylDragon @fujitatomoya, Updated with underlying implementations first:).

[fujitatomoya]

@leeminju531 thanks for putting the effort on this.

i will do the another review once they are ready, so please let me know.