Github rest api post label gives error for array input
From my understanding of the docs, you should directly send an array (which is valid JSON), without wrapping it in an object. That is ["bug"] instead of {"labels": ["bug"]}.

So, the proper request should be:

curl -X POST -u githuser:gittoken \
    https://api.github.mycompany.com/repos/team/repo/issues/560/labels \
    -H "Content-type: application/json" -k \
    -d '["bug"]' \
    -H "Accept: application/json"