MM-11781: Basic Data Export Command Line. (#9296)

* MM-11781: Basic Data Export Command Line.

* ChannelStore new unit tests.

* TeamStore new unit tests.

* Unit test for new UserStore function.

* Unit tests for post store new methods.

* Review fixes.

* Fix duplicate command name.

model/team_member.go

@@ -26,6 +26,11 @@ type TeamUnread struct {
 	MentionCount int64  `json:"mention_count"`
 }
 
+type TeamMemberForExport struct {
+	TeamMember
+	TeamName string
+}
+
 func (o *TeamMember) ToJson() string {
 	b, _ := json.Marshal(o)
 	return string(b)