Add a consumer to a group
-------------------------
Endpoint:
	https://auth.datasetu.org/auth/v1/group/add
Description:
	This API is used to add a consumer to a group.
	Groups are useful in setting access control polcies where access to
	resources is given to a group of consumers.
	This is done using the "consumer-in-group(group-name)" function in
	the aperture policy when using the "/acl/set" API.
Called by:
	A "data provider" with a valid class-3 or above certificate.
Methods:
	POST
Headers:
	content-type : "application/json"
Body in JSON format:
	{
		"group"	: <a valid group name created by the user>			
		"consumer"	: <the consumer's email-id, which is to be added to the group>	
		"valid-till"	: <how long (in hours) the consumer will be in the group>	
	}
	Note: If the "group" doesn't exist, it will be created automatically.
Using pyIUDX SDK:
	from pyIUDX.auth import auth
	iudx_auth = auth.Auth("certificate.pem","private-key.pem")
	# add user@domain.com to confidential group for 1 hour
	iudx_auth.add_consumer_to_group("user@domain.com","confidential",1)
CURL example:
	Request:
		curl -XPOST https://auth.datasetu.org/auth/v1/group/add
			--cert certificate.pem --key private-key.pem
			-H 'content-type: application/json'
			-d '{"group" : "confidential","consumer" : "user@domain.com", "valid-till" : 3600}'
	Response:
		200 OK
		content-type : "application/json"
		{
			"success" : true
		}
See also:
	acl set API:
		http://auth.datasetu.org/acl-set.html
	group delete API:
		http://auth.datasetu.org/group-delete.html
	group list API:
		http://auth.datasetu.org/group-list.html