add database migration

[awpt1mus]

• add support for migrations
• convert existing single schema into a migration that can be applied or undo when needed
• add commands into make file to make it convenient to apply / reset / undo migrations
• add scripts to seed dummy data

[awpt1mus]

will add database seeding in separate task, need to discuss what is considered standard practice - whether it should be implemented as Go code or raw INSERT statements in .sql files,