[Bug] (CalDav) Shared calendar event invitations Accept/Decline not working

[SebastianKrupinski]

Steps to reproduce

1. Create shared calendar as user A and share with user B and C
2. Create event in shared calendar as User B and invite User C
3. Accept invitation from the email as User C

Expected behavior

When clicking Accept/Decline the participant status in the event in the shared calendar and personal calendar should be updated.

Actual behaviour

Currently the participant status is only updated in the personal calendar.

Calendar app version

No response

CalDAV-clients used

NC UI

Browser

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Client operating system

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Server operating system

No response

Web server

None

Database engine version

None

PHP engine version

None

Nextcloud version

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Updated from an older installed version or fresh install

None

List of activated apps

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Nextcloud configuration

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Web server error log

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Log file

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Browser log

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Additional info

No response

[SebastianKrupinski]

Test results.

[SebastianKrupinski]

Issue is caused by the OCA\DAV\Controller\InvitationResponseController::buildITipResponse() method. The generated iTIp message is formatted incorrectly, as the sender and recipient are the same user.

The iTip message should be from sender "user1" to recipient "user3" (the organizer)