Python API Ros2idl decoding support or workaround

[tgrubes]

This has been previously mentioned in #1095, but the mcap_ros2.decoder module does not work with schemas written in IDL.

There seems to be a rosidl parser that predates the issue above, but no work had been done on it since the initial commit.

Has there been any progress on this since #1095 was posted? If not, are there any potential workarounds?

I'm fairly unfamiliar with how messages are encoded and decoded, but I see that they are all in cdr. To what extent does the schema type affect the message encoding? For the same contents and structure, would ros2msg and ros2idl defined messages result in the same cdr composition? If so, is it possible to replace an mcap's recorded idl schema with an equivalent rosmsg description to decode the relevant messages?