[ASC] Add users to a test group of a specific app

[Blackjacx]

Code to delete user in specific groups:

curl -g -s -X DELETE "$url/betaTesters/$uid/relationships/betaGroups" -H "$json_content_type" -H "Authorization: $ASC_AUTH_HEADER" -d '{"data": [{ "id": "'$gid'", "type": "betaGroups" }] }'

To uniquely identify the correct group to remove the given tester from just specify:

• the group name
• the app id <- this is the new stuff: add a parameter --app-ids (-a) to beta-testers add cmd