Add explicit rmf_traffic dependencies

[Plumezz]

This PR adds explicit rmf_traffic dependency declarations for rmf_task and rmf_task_sequence.

Both packages directly use rmf_traffic types in their public headers and implementation code. For example:

• rmf_task includes rmf_traffic/Time.hpp, rmf_traffic/Trajectory.hpp, and rmf_traffic/agv/Planner.hpp in request/task planning headers.
• rmf_task_sequence uses rmf_traffic::Time, rmf_traffic::Duration, and rmf_traffic::agv::Plan::Goal in its public task, activity, and event APIs.

Currently these packages can receive rmf_traffic transitively through other RMF dependencies, but the direct source usage is not fully reflected in package metadata.

Changes:

• Add <depend>rmf_traffic</depend> to rmf_task/package.xml.
• Add <depend>rmf_traffic</depend> to rmf_task_sequence/package.xml.
• Add find_package(rmf_traffic REQUIRED) to rmf_task_sequence/CMakeLists.txt.
• Link rmf_task_sequence against rmf_traffic::rmf_traffic.
• Link rmf_task against rmf_traffic::rmf_traffic.
• Add find_dependency(rmf_traffic) to rmf_task_sequence's exported CMake config.

rmf_task already had find_package(rmf_traffic REQUIRED) and find_dependency(rmf_traffic), so the change there only updates package.xml to match the existing CMake dependency.

[luca-della-vedova]

I'm not very familiar with this part of the code but it seems this is only to generate the header with the schema as a string, so we might not need to add any dependency?

[Plumezz]

Thanks for pointing this out.

You are right that the schema header generation itself does not need rmf_traffic. My intention here was not to support the schema generation step, but to export the dependency required by the public C++ API of rmf_task_sequence.

rmf_task_sequence exposes rmf_traffic types in public headers, for example rmf_traffic::Time, rmf_traffic::Duration, and rmf_traffic::agv::Plan::Goal. So downstream packages that call find_package(rmf_task_sequence) may also need the rmf_traffic dependency to be discoverable.

That said, I also noticed I used find_package(rmf_traffic REQUIRED) in the config template, which should be find_dependency(rmf_traffic) to match the other exported dependencies. I will update that.

[luca-della-vedova]

I noticed that rmf_task is missing this dependency in its library, should it be added there as well?

[Plumezz]

Good point, yes, I agree. I think it should be added as well.

I will update the PR.