Keep id when moving from message to message_read table
When a message is marked as read, it is moved from the message table to the message_read table with a new id

this change keeps the same id accross the message -> message_read table

This issue is an in-between step towards merging the message / message_read table (if the tables are merged, the id's would be the same)
but it stands alone and is helpful if the two tables are not merged