Add curl examples to operator-http-api

[nhandler]

When reading this document, many people will want to test out the
requests against their own environment. Providing curl examples will
help assist with this task.

[vinodkone]

@nhandler Thanks for doing this! Awesome. Do I take it that you tested all these commands? Also, is the EOF required in all the curl commands?

[vinodkone]

LGTM!

[greggomann]

@nhandler similar to Vinod's comment: I think we could probably get away without the heredoc notation, to get rid of the EOFs?

i.e.:

curl -i \
  -X POST http://<masterhost>:5050/api/v1 \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -d '
{
  "type": "GET_HEALTH"
}'

This works when I test it in bash anyway :)
I think it makes sense to avoid the EOFs in this context since these are documentation as well as examples, it will help reduce noise and make the essential information easier to identify.

[vinodkone]

@nhandler If you can update the PR, I'll commit it ASAP.

[greggomann]

@nhandler we were reviewing PRs today and came across this one - do you have a cycle to update real quick?