Webhook returns 400 Bad Request

[simonamor]

Thanks for writing these and making them available.
The Bad Request problem turned out to be due to two separate issues.

First, the NAGIOS_xxx environment variables weren't being defined. I fixed this by changing (in nagios.cfg):
enable_environment_macros=0
to read
enable_environment_macros=1

My nagios installation is fairly small so this is ok but the config has a warning that this may cause problems with larger installs.

Second issue was that it wasn't liking the default format date in NAGIOS_SHORTDATETIME

To fix this I changed (in nagios.cfg):
date_format=us
to read
date_format=iso8601

Might need to mention these in the README.