Duplicate Video Token in Migration

[dennis531]

Version
main

Describe the bug
The random token generation tries to set the same token for all videos in

studip-opencast-plugin/migrations/100_migrate_missing_cw_blocks.php

Line 16 in 3ebf7db

$db->exec('UPDATE oc_video SET token = LOWER(SUBSTRING(MD5(RAND()), 1, 12))

Also, generating tokens in this way may cause collisions, and not just in this particular location.

To Reproduce
Steps to reproduce the behavior:

1. Install plugin version 3 on a system with plugin version 2
2. See the following exception

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'd4e466ef1544' for key 'token'

Expected behavior
The migration should set a distinct token for each video.