Use notice instead of error for expected "errors"

Notice() is like Error(), but:

- the message is not sent to the error log (and Sentry)
- the message sent to the room is not prefixed with `ERROR: `

bot/bot.go

@@ -59,6 +59,14 @@ func (b *Bot) Error(ctx context.Context, roomID id.RoomID, message string, args
 	}
 }
 
+// Notice sends a notice message to the matrix room
+func (b *Bot) Notice(ctx context.Context, roomID id.RoomID, message string, args ...interface{}) {
+	b.lp.Send(roomID, &event.MessageEventContent{
+		MsgType: event.MsgNotice,
+		Body:    fmt.Sprintf(message, args...),
+	})
+}
+
 // Start performs matrix /sync
 func (b *Bot) Start() error {
 	if err := b.migrate(); err != nil {

bot/mailbox.go

@@ -54,7 +54,7 @@ func (b *Bot) getMailbox(ctx context.Context, evt *event.Event) {
 	}
 
 	if cfg.Mailbox == "" {
-		b.Error(span.Context(), evt.RoomID, "mailbox name is not set")
+		b.Notice(span.Context(), evt.RoomID, "mailbox name is not set")
 		return
 	}
 
@@ -87,7 +87,7 @@ func (b *Bot) setMailbox(ctx context.Context, evt *event.Event, mailbox string)
 	}
 
 	if !cfg.Allowed(b.noowner, evt.Sender) {
-		b.Error(span.Context(), evt.RoomID, "you don't have permission to do that")
+		b.Notice(span.Context(), evt.RoomID, "you don't have permission to do that")
 		return
 	}
 

bot/owner.go

@@ -28,7 +28,7 @@ func (b *Bot) getOwner(ctx context.Context, evt *event.Event) {
 	}
 
 	if cfg.Owner == "" {
-		b.Error(span.Context(), evt.RoomID, "owner is not set yet")
+		b.Notice(span.Context(), evt.RoomID, "owner is not set yet")
 		return
 	}
 
@@ -52,7 +52,7 @@ func (b *Bot) setOwner(ctx context.Context, evt *event.Event, owner string) {
 	}
 
 	if !cfg.Allowed(b.noowner, evt.Sender) {
-		b.Error(span.Context(), evt.RoomID, "you don't have permission to do that")
+		b.Notice(span.Context(), evt.RoomID, "you don't have permission to do that")
 		return
 	}