[MM-34303] Add team ID to response when linking a channel to a group (#17576)

* add team ID to channel group response

Co-authored-by: Benjamin Cooke <benjamincooke@Benjamins-MacBook-Pro.local>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/group_syncable.go

@@ -60,14 +60,14 @@ func (syncable *GroupSyncable) UnmarshalJSON(b []byte) error {
 	if err != nil {
 		return err
 	}
+	var channelId string
+	var teamId string
 	for key, value := range kvp {
 		switch key {
 		case "team_id":
-			syncable.SyncableId = value.(string)
-			syncable.Type = GroupSyncableTypeTeam
+			teamId = value.(string)
 		case "channel_id":
-			syncable.SyncableId = value.(string)
-			syncable.Type = GroupSyncableTypeChannel
+			channelId = value.(string)
 		case "group_id":
 			syncable.GroupId = value.(string)
 		case "auto_add":
@@ -75,30 +75,40 @@ func (syncable *GroupSyncable) UnmarshalJSON(b []byte) error {
 		default:
 		}
 	}
+	if channelId != "" {
+		syncable.TeamID = teamId
+		syncable.SyncableId = channelId
+		syncable.Type = GroupSyncableTypeChannel
+	} else {
+		syncable.SyncableId = teamId
+		syncable.Type = GroupSyncableTypeTeam
+	}
 	return nil
 }
 
 func (syncable *GroupSyncable) MarshalJSON() ([]byte, error) {
 	type Alias GroupSyncable
-
 	switch syncable.Type {
 	case GroupSyncableTypeTeam:
 		return json.Marshal(&struct {
-			TeamID          string `json:"team_id"`
-			TeamDisplayName string `json:"team_display_name,omitempty"`
-			TeamType        string `json:"team_type,omitempty"`
+			TeamID          string            `json:"team_id"`
+			TeamDisplayName string            `json:"team_display_name,omitempty"`
+			TeamType        string            `json:"team_type,omitempty"`
+			Type            GroupSyncableType `json:"type,omitempty"`
 			*Alias
 		}{
 			TeamDisplayName: syncable.TeamDisplayName,
 			TeamType:        syncable.TeamType,
 			TeamID:          syncable.SyncableId,
+			Type:            syncable.Type,
 			Alias:           (*Alias)(syncable),
 		})
 	case GroupSyncableTypeChannel:
 		return json.Marshal(&struct {
-			ChannelID          string `json:"channel_id"`
-			ChannelDisplayName string `json:"channel_display_name,omitempty"`
-			ChannelType        string `json:"channel_type,omitempty"`
+			ChannelID          string            `json:"channel_id"`
+			ChannelDisplayName string            `json:"channel_display_name,omitempty"`
+			ChannelType        string            `json:"channel_type,omitempty"`
+			Type               GroupSyncableType `json:"type,omitempty"`
 
 			TeamID          string `json:"team_id,omitempty"`
 			TeamDisplayName string `json:"team_display_name,omitempty"`
@@ -109,6 +119,7 @@ func (syncable *GroupSyncable) MarshalJSON() ([]byte, error) {
 			ChannelID:          syncable.SyncableId,
 			ChannelDisplayName: syncable.ChannelDisplayName,
 			ChannelType:        syncable.ChannelType,
+			Type:               syncable.Type,
 
 			TeamID:          syncable.TeamID,
 			TeamDisplayName: syncable.TeamDisplayName,