* Created message export scheduled task
* Added CLI command to immediately kick off an export job
* Added email addresses for users joining and leaving the channel to the export
* Added support for both MySQL and PostgreSQL
* Fixing gofmt error
* Added a new ChannelMemberHistory store and associated tests
* Updating the ChannelMemberHistory channel as users create/join/leave channels
* Added user email to the message export object so it can be included in the actiance export xml
* Don't fail to log a leave event if a corresponding join event wasn't logged
* Adding copyright notices
* Adding message export settings to daily diagnostics report
* Added System Console integration for message export
* Cleaned up TODOs
* Made batch size configurable
* Added export from timestamp to CLI command
* Made ChannelMemberHistory table updates best effort
* Added a context-based timeout option to the message export CLI
* Minor PR updates/improvements
* Removed unnecessary fields from MessageExport object to reduce query overhead
* Removed JSON functions from the message export query in an effort to optimize performance
* Changed the way that channel member history queries and purges work to better account for edge cases
* Fixing a test I missed with the last refactor
* Added file copy functionality to file backend, improved config validation, added default config values
* Fixed file copy tests
* More concise use of the testing libraries
* Fixed context leak error
* Changed default export path to correctly place an 'export' directory under the 'data' directory
* Can't delete records from a read replica
* Fixed copy file tests
* Start job workers when license is applied, if configured to do so
* Suggestions from the PR
* Moar unit tests
* Fixed test imports
* don't use global app for api / api4 tests
* put sleep back. we're gonna have to do some goroutine wrangling
* fix oauth test config assumptions
* jobs package, i'm comin' for you next
* app test fix
* try increasing sleep a little
* tie back-end plugins together
* fix comment typo
* add tests and a bit of polish
* tests and polish
* add test, don't let backend executable paths escape the plugin directory
