[PB-6385] Add migration to remove constraint

[TamaraFinogina]

Migration to remove ['user_id', 'room_id'] uniqueness constraint from the database.

To fix user kick out the idea is to:

1. Each joinCall will create a record in the database with (id, user_id, room_id, jitsi_id) and return id to the user ← this is why the constraint should be removed
2. User stores id in sessionStorage
3. When user is kicked out - Jitsi webhook sends jitsi_id for deletion
4. When user is kicked out - meet-web sends leaveCall with id

3 and 4 will result in deletion of the same line (whichever arrives first) and mostly done for redundancy.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sg-gs]

Migration run @TamaraFinogina

Sequelize CLI [Node: 22.16.0, CLI: 6.6.2, ORM: 6.37.6]

Loaded configuration file "src/config/sequelize.js".
Using environment "production".
== 20260520142639-remove-unique-constraint-to-room-users: migrating =======
== 20260520142639-remove-unique-constraint-to-room-users: migrated (0.024s)

Done in 0.84s.