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

utils/file_backend_s3.go

@@ -95,6 +95,23 @@ func (b *S3FileBackend) ReadFile(path string) ([]byte, *model.AppError) {
 	}
 }
 
+func (b *S3FileBackend) CopyFile(oldPath, newPath string) *model.AppError {
+	s3Clnt, err := b.s3New()
+	if err != nil {
+		return model.NewAppError("copyFile", "api.file.write_file.s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	source := s3.NewSourceInfo(b.bucket, oldPath, nil)
+	destination, err := s3.NewDestinationInfo(b.bucket, newPath, nil, s3CopyMetadata(b.encrypt))
+	if err != nil {
+		return model.NewAppError("copyFile", "api.file.write_file.s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	if err = s3Clnt.CopyObject(destination, source); err != nil {
+		return model.NewAppError("copyFile", "api.file.move_file.copy_within_s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	return nil
+}
+
 func (b *S3FileBackend) MoveFile(oldPath, newPath string) *model.AppError {
 	s3Clnt, err := b.s3New()
 	if err != nil {
@@ -107,7 +124,7 @@ func (b *S3FileBackend) MoveFile(oldPath, newPath string) *model.AppError {
 		return model.NewAppError("moveFile", "api.file.write_file.s3.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 	if err = s3Clnt.CopyObject(destination, source); err != nil {
-		return model.NewAppError("moveFile", "api.file.move_file.delete_from_s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+		return model.NewAppError("moveFile", "api.file.move_file.copy_within_s3.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 	if err = s3Clnt.RemoveObject(b.bucket, oldPath); err != nil {
 		return model.NewAppError("moveFile", "api.file.move_file.delete_from_s3.app_error", nil, err.Error(), http.StatusInternalServerError)