It was a great time, with wonderful presentations about TrailheaDX by James Loghry and Developing with Security in Mind by Davin Leier and Barry Bakunowicz.
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Links
Here are the links that were on the last slide of the presentation.
No? On the Salesforce DX page it says to turn on the Dev Hub in your Production or Business Org. (source)
Can you restrict Developers from using Salesforce DX on a Production Org?
By default the permissions to related to Salesforce DX are assigned to the System Administrator profile. (source) These permisions can be assigned to non-System Administrators through permission sets. (source)
Is there a side effect of enabling the Dev Hub and not using it?
Aside from the System Administrators having something else to ignore I am unaware of any negative side effects of not using the Dev Hub features once they are enabled. (no source)
When data is loaded from JSON files using force:data:tree:import does it maintain relationships?
Yes, this data can contain master-detail relationships. (source)