Support migrations for the TinyDB repository

[lyz-code]

Description

Even though TinyDB is meant to be schemaless, we could have a tool like yoyo for sql to do changes in the existent objects to conform to the new schema.

Possible Solution

Create a TinyDB extension that can read a list of files from a migrations directory and execute the steps defined there. Each file will have a hash, and the latest applied can be saved in the _tinydb_migrations table in the database.

I'd copy how yoyo has already solved the issue.