Constants reference

Following constants are importable from ariadne.constants module:

`CONTENT_TYPE_JSON`

CONTENT_TYPE_JSON = 'application/json; charset=UTF-8'

CONTENT_TYPE_TEXT_HTML = 'text/html; charset=UTF-8'

CONTENT_TYPE_TEXT_PLAIN = 'text/plain; charset=UTF-8'

DATA_TYPE_JSON = 'application/json'

DATA_TYPE_MULTIPART = 'multipart/form-data'