MM-28249 Auto follow threads (#15878)

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/config.go

@@ -347,6 +347,7 @@ type ServiceSettings struct {
 	EnableLocalMode                                   *bool
 	LocalModeSocketLocation                           *string
 	EnableAWSMetering                                 *bool
+	ThreadAutoFollow                                  *bool `access:"experimental"`
 }
 
 func (s *ServiceSettings) SetDefaults(isUpdate bool) {
@@ -764,6 +765,11 @@ func (s *ServiceSettings) SetDefaults(isUpdate bool) {
 	if s.EnableAWSMetering == nil {
 		s.EnableAWSMetering = NewBool(false)
 	}
+
+	if s.ThreadAutoFollow == nil {
+		s.ThreadAutoFollow = NewBool(true)
+	}
+
 }
 
 type ClusterSettings struct {

model/thread.go

@@ -22,3 +22,16 @@ func (o *Thread) ToJson() string {
 func (o *Thread) Etag() string {
 	return Etag(o.PostId, o.LastReplyAt)
 }
+
+type ThreadMembership struct {
+	PostId      string `json:"post_id"`
+	UserId      string `json:"user_id"`
+	Following   bool   `json:"following"`
+	LastViewed  int64  `json:"last_view_at"`
+	LastUpdated int64  `json:"last_update_at"`
+}
+
+func (o *ThreadMembership) ToJson() string {
+	b, _ := json.Marshal(o)
+	return string(b)
+}