Add leaderboard versions

[Manuel O]

Outcomes

• Customers should be able to create multiple versions of a leaderboard.
• The public leaderboard view should allow users to view any published version of a leaderboard.
• Customers should be able to push data to any version of a leaderboard.

What it should do

• User can create draft versions,
• publish draft versions as public,
• and unpublish published leaderboards back into draft state.
• take snapshots at any time point

[Neeraj Kashyap]

Snapshots at any point in time is ambiguous. Versions are snapshots.