Enhance SNS Publish Batch

[dormesica]

Is your feature request related to a problem? Please describe

SNS Publish Batch command is not automatically enhanced

Describe the solution you'd like to see

Same as Message Attributes are added to publish command input, it should be also be added to the different messages published with Publish Batch command.

Describe alternatives you've considered

Additional context

[dormesica]

Hi @pichlermarc
Since I need this support I attempted to open a PR for solving this issue (#2710).

I wrote a test for the changes I've made, however the test fails on line 271 on this assertion.

expect(publishSpans.length).toBe(1);

Since I'm new here, perhaps someone could point me to what I'm missing so that I can solve this?