fix(comment): add validation check for the max comment length

Resolves https://vikunja.sentry.io/issues/6441922105/events/245b8f1de3e64951a108e2f6cb654c58/

pkg/models/task_comments.go

@@ -20,7 +20,6 @@ import (
 	"time"
 
 	"code.vikunja.io/api/pkg/db"
-
 	"code.vikunja.io/api/pkg/events"
 	"code.vikunja.io/api/pkg/user"
 	"code.vikunja.io/api/pkg/web"
@@ -32,7 +31,7 @@ import (
 // TaskComment represents a task comment
 type TaskComment struct {
 	ID       int64      `xorm:"autoincr pk unique not null" json:"id" param:"commentid"`
-	Comment  string     `xorm:"text not null" json:"comment"`
+	Comment  string     `xorm:"text not null" json:"comment" valid:"dbtext,required"`
 	AuthorID int64      `xorm:"not null" json:"-"`
 	Author   *user.User `xorm:"-" json:"author"`
 	TaskID   int64      `xorm:"not null" json:"-" param:"task"`

pkg/routes/validation.go

@@ -17,6 +17,9 @@
 package routes
 
 import (
+	"strings"
+
+	"code.vikunja.io/api/pkg/config"
 	"code.vikunja.io/api/pkg/models"
 
 	"github.com/asaskevich/govalidator"
@@ -26,9 +29,25 @@ import (
 type CustomValidator struct{}
 
 func init() {
-	govalidator.TagMap["time"] = govalidator.Validator(func(str string) bool {
+	govalidator.TagMap["time"] = func(str string) bool {
 		return govalidator.IsTime(str, "15:04")
-	})
+	}
+
+	// Custom validator for database TEXT fields that adapts to the database being used
+	govalidator.TagMap["dbtext"] = func(str string) bool {
+		// Get the current database dialect
+		dialect := strings.ToLower(config.DatabaseType.GetString())
+
+		// Default limit for MySQL and unknown databases (65KB safely under TEXT limit)
+		maxLength := 65000
+
+		// For databases that support larger text fields
+		if dialect == "postgres" || dialect == "sqlite" || dialect == "sqlite3" {
+			maxLength = 1048576 // ~1MB limit for PostgreSQL and SQLite
+		}
+
+		return len(str) <= maxLength
+	}
 }
 
 // Validate validates stuff