autoware_msgs Finalization

[xmfcx]

The finalized messages will reside in the https://github.com/autowarefoundation/autoware_msgs repository.

Related issues:

• Merge map_db with map_file. #84
• Change the reference of autoware_auto_msgs autoware_universe#142

We can discuss here what messages to put there and what their final forms should be.

Autoware Universe currently uses tier4's fork of autoware_auto_msgs.

tier4's fork of autoware_auto_msgs are ported from autoware_auto_msgs.

We will take the necessary messages from the tier4's fork of autoware_auto_msgs and modify & finalize them for this repository and replace the old messages over time.

[isamu-takagi]

I started implementing the API prototype to help discussion of API. So, I plan to add autoware_ad_api_msgs package.

First, add this package to the autoware.universe repository. This is because there will be many PRs for prototyping and each PR will need to add messages. It's a waste of time to make two PRs each time. Finally, move the package to the message repository when the message is stable.

[kenji-miyake]

I'll add some supplemental comments.

First, the version API, which must be very stable, will be merged in this PR.
autowarefoundation/autoware_universe#704

Then, TIER IV will implement prototypes, which will be merged with TIER IV's internal reviews and will be the AD API v0 (or v1 would be better?).

After that, TIER IV will ask other contributors to review them and update messages based on the reviews, which will be v1.

@xmfcx cc @mitsudome-r Please let us know if you have any questions or feedback.

[kenji-miyake]

I'll link to related information.
https://gitlab.com/autowarefoundation/autoware.auto/AutowareAuto/-/issues/1421