chore: update activity store definition

store/activity.go

@@ -2,8 +2,30 @@ package store
 
 import (
 	"context"
+
+	storepb "github.com/usememos/memos/proto/gen/store"
 )
 
+type ActivityType string
+
+const (
+	ActivityTypeMemoComment ActivityType = "MEMO_COMMENT"
+)
+
+func (t ActivityType) String() string {
+	return string(t)
+}
+
+type ActivityLevel string
+
+const (
+	ActivityLevelInfo ActivityLevel = "INFO"
+)
+
+func (l ActivityLevel) String() string {
+	return string(l)
+}
+
 type Activity struct {
 	ID int32
 
@@ -12,9 +34,9 @@ type Activity struct {
 	CreatedTs int64
 
 	// Domain specific fields
-	Type    string
-	Level   string
-	Payload string
+	Type    ActivityType
+	Level   ActivityLevel
+	Payload *storepb.ActivityPayload
 }
 
 type FindActivity struct {