MM-52216: Trim errors (#23040)

https://mattermost.atlassian.net/browse/MM-52216
```release-note
NONE
```

server/model/utils.go

@@ -251,6 +251,8 @@ type AppError struct {
 	wrapped       error
 }
 
+const maxErrorLength = 1024
+
 func (er *AppError) Error() string {
 	var sb strings.Builder
 
@@ -276,7 +278,11 @@ func (er *AppError) Error() string {
 		sb.WriteString(err.Error())
 	}
 
-	return sb.String()
+	res := sb.String()
+	if len(res) > maxErrorLength {
+		res = res[:maxErrorLength] + "..."
+	}
+	return res
 }
 
 func (er *AppError) Translate(T i18n.TranslateFunc) {

server/model/utils_test.go

@@ -116,6 +116,13 @@ func TestAppErrorRender(t *testing.T) {
 		aerr := NewAppError("here", "message", nil, "details", http.StatusTeapot).Wrap(fmt.Errorf("my error (%w)", fmt.Errorf("inner error")))
 		assert.EqualError(t, aerr, "here: message, details, my error (inner error)")
 	})
+
+	t.Run("MaxLength", func(t *testing.T) {
+		str := strings.Repeat("error", 65536)
+		msg := "msg"
+		aerr := NewAppError("id", msg, nil, str, http.StatusTeapot).Wrap(errors.New(str))
+		assert.Len(t, aerr.Error(), maxErrorLength+len(msg))
+	})
 }
 
 func TestAppErrorSerialize(t *testing.T) {