Auto assign default roles for a team to its users

[mithmatt]

Feature
#2762

Describe the task
When user <> team relationship is updated (add/delete) also ensure user <> role relationship is updated (add/delete) based on the team's default roles.

[harshach]

@mithmatt if you are planning to add this in 0.9 release, let us know. we can add UI related tickets and mark the Project as Release 0.9.0

[mithmatt]

@harshach Yes, this is ready for UI work - I was about to flag this as potential candidate for 0.9 when I merge #2947

UI ticket #2884