Version 4

Highlights

Updates Django to 2.1.5
Updates Python to Python 3.7
New checkin version 3 endpoint.
- This new checkin requires new sal-scripts to work with it.
- The old checkin is deprecated and old sal-scripts will not work.
- If you have plugins that require a checkin_processor, the structure of the data passed to them has changed, and you'll need to update your code to account for this. See the Wiki regarding checkin processors.
- Checkin is a lot faster.
- Ongoing maintenance tasks have been moved to a background task rather than the checkin code.
Management Sources and Managed Items (allows arbitrary sources of management to add checkin data for display in various places around Sal).
Messages: Any checkin module can add messages (debug, warning, error, etc) to their results.
- New Messages dashboard plugin, shows counts of common errors and warnings, with links to machine list views of affected devices.
More information about installed Apple updates.
Hot-nasty performance improvements.
Visibility of Munki optional installs.

Distribute the new sal-scripts (and any optional checkin-modules desired) to clients.
Update your Sal instance to version 4.
Custom plugins:
- If you still have an "old-style" plugin, you need to update it!
- If your plugin has a "checkin-processor", you'll need to update it to use the new checkin submission format.

Code supporting old-school plugins has been removed.
Adds default port value for memcached (thanks @gavinelder )
PluginManager refactored to the singleton pattern; this should dramatically reduce plugin code busywork and startup times.
Numerous python -> database query changes to improve bottlenecks (@sheagcraig @natewalck FTW)
Standardized access requirements for settings views (Requires GA status).