PLT-7503: Create Message Export Scheduled Task and CLI Command (#7612)

* 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

app/app.go

@@ -48,6 +48,7 @@ type App struct {
 	Elasticsearch    einterfaces.ElasticsearchInterface
 	Emoji            einterfaces.EmojiInterface
 	Ldap             einterfaces.LdapInterface
+	MessageExport    einterfaces.MessageExportInterface
 	Metrics          einterfaces.MetricsInterface
 	Mfa              einterfaces.MfaInterface
 	Saml             einterfaces.SamlInterface
@@ -198,6 +199,12 @@ func RegisterJobsDataRetentionJobInterface(f func(*App) ejobs.DataRetentionJobIn
 	jobsDataRetentionJobInterface = f
 }
 
+var jobsMessageExportJobInterface func(*App) ejobs.MessageExportJobInterface
+
+func RegisterJobsMessageExportJobInterface(f func(*App) ejobs.MessageExportJobInterface) {
+	jobsMessageExportJobInterface = f
+}
+
 var jobsElasticsearchAggregatorInterface func(*App) ejobs.ElasticsearchAggregatorInterface
 
 func RegisterJobsElasticsearchAggregatorInterface(f func(*App) ejobs.ElasticsearchAggregatorInterface) {
@@ -222,6 +229,12 @@ func RegisterLdapInterface(f func(*App) einterfaces.LdapInterface) {
 	ldapInterface = f
 }
 
+var messageExportInterface func(*App) einterfaces.MessageExportInterface
+
+func RegisterMessageExportInterface(f func(*App) einterfaces.MessageExportInterface) {
+	messageExportInterface = f
+}
+
 var metricsInterface func(*App) einterfaces.MetricsInterface
 
 func RegisterMetricsInterface(f func(*App) einterfaces.MetricsInterface) {
@@ -267,6 +280,9 @@ func (a *App) initEnterprise() {
 			}
 		})
 	}
+	if messageExportInterface != nil {
+		a.MessageExport = messageExportInterface(a)
+	}
 	if metricsInterface != nil {
 		a.Metrics = metricsInterface(a)
 	}
@@ -289,6 +305,9 @@ func (a *App) initJobs() {
 	if jobsDataRetentionJobInterface != nil {
 		a.Jobs.DataRetentionJob = jobsDataRetentionJobInterface(a)
 	}
+	if jobsMessageExportJobInterface != nil {
+		a.Jobs.MessageExportJob = jobsMessageExportJobInterface(a)
+	}
 	if jobsElasticsearchAggregatorInterface != nil {
 		a.Jobs.ElasticsearchAggregator = jobsElasticsearchAggregatorInterface(a)
 	}