Migrate Server from one AD to new one

Hello all,

At my company we are planning to migrate a SysAid server from one Active Directory to a new one.
In this scenario some users have a new username in the new AD.
Someone can give us clues on how we can guide the migration process, maintaining the consistency of information in the database in the new server, in order to convert the old usernames to new usernames, without losing any past records relationship.