[SUN-887] Initial joint values are read when the hardware interface starts

[tgaspar]

Description

This PR adds code that reads joint state values from RWS before the hardware interface is started. It is important to note that the code introduced here does not make use of the existing RWS managers that would be available vie abb_librws because those are incompatible with RWS2.0. For the sake of not complicating things, I added a simple method that makes the HTTP GET request to the correct address to retrieve the joint values.

Some reading material regarding the issue:

• Robot arm goes to zero position the moment ros2_control is started
• Add support for RWS 2.0

Test plan

The test plan revolves mainly around making sure everything builds. The functionality will be tested by me on the real robot. Some additional changes might come into place after the test are done. However, the bulk of the work is here.

Checklist for Reviewers

Reviewer 1: @fgrcar
Reviewer 2: @JenniferBuehler

Before a PR to this repo can get approved and merged, the following needs to be checked by both reviewers:

• The test plan was executed and verified by:
  • Reviewer 1
  • Reviewer 2
• Documentation added, function/classes headers clean?
  • Reviewer 1 check
  • Reviewer 2 check
• Has the README.md been updated, or not required?
  • Reviewer 1 check
  • Reviewer 2 check
• Has the CHANGELOG been updated?
  • Reviewer 1 check
  • Reviewer 2 check
• Have unit tests been added where needed?
  • Reviewer 1 check
  • Reviewer 2 check
• Any testing not covered by unit tests was done manually by the reviewers.
  • Reviewer 1
  • Reviewer 2
• Version ticks in package.xml, CMakeLists.txt and/or setup.py were made.
  • Reviewer 1 check
  • Reviewer 2 check
• Licensing updates were added, or not required.
  • Reviewer 1 check
  • Reviewer 2 check
• New dependencies added to requirements.txt, setup.py and package.xml - or: not applicable.
  • Reviewer 1 check
  • Reviewer 2 check

[JenniferBuehler]

I built it, it works. Nice!

I have general concerns about how we keep this in sync with upstream (or is our fork so far evolved?) but that's a separate question to this PR. I asked on slack already :)

[JenniferBuehler]

No idea why I can't tick the checkmarks on the PR description... maybe it's the recent apt upgrade result that I was semi-forced to do and has already given me a bit of headache (with nvidia, whatta surprise)

[fgrcar]

I can imagine how painful this was 🫂.
Check the comments and you're good to go.

[fgrcar]

Btw, I can't tick the checkboxes in the description, so something is wrong with the permissions I guess.