External images in appointment e-mail messages

Steps to reproduce

With calendar invitations sending enabled create appointment and switch to e-mail reader (i.e. Thunderbird) to see that external content is blocked there.

Expected behavior

E-mail messages with calendar events (invitations, upgrades, cancellations) should not contain any links to external images. HTML tags with external images should be removed from message HTML content to simplify things (embedding images as attachments will make messages bigger and should be avoided also).

Actual behaviour

Every e-mail message send from calendar (invitation, cancellation) contains 3 HTML img tags with src pointing to nc installation i.e.:

https://nextcloud.domain.here/core/img/logo/logo.png?v=3
https://nextcloud.domain.here/core/img/caldav/title.png
https://nextcloud.domain.here/core/img/caldav/time.png

Such images are not necessary for event communication to work and may generate problems (mail reader warnings, antispam filter reactions, etc.).

Calendar app version

3.4.0

CalDAV-clients used

No response

Browser

No response

Client operating system

No response

Server operating system

No response

Web server

No response

Database engine version

No response

PHP engine version

No response

Nextcloud version

24.0.2

Updated from an older installed version or fresh install

No response

List of activated apps

No response

Nextcloud configuration

No response

Web server error log

No response

Log file

No response

Browser log

No response

Additional info

No response

Reproduce the issue by sending a calendar invitation, cancellation, or upgrade and opening the message in an email reader such as Thunderbird. Trace where calendar email HTML is generated and remove the external image tags; done means these messages contain no links to external images while preserving their event information.