MM-11649: Fix caching issue in channel API endpoints. (#9345)

This fixes an issue where the cached Channel objects would contain data
from a failed update when the update to the database failed.

model/channel.go

@@ -59,6 +59,9 @@ type ChannelPatch struct {
 
 func (o *Channel) DeepCopy() *Channel {
 	copy := *o
+	if copy.SchemeId != nil {
+		copy.SchemeId = NewString(*o.SchemeId)
+	}
 	return &copy
 }