chore: enable version-specific db migration

[masaaania]

Fixes #685

[masaaania]

Current Status

• This PR is in wip status.
• This PR conforms to the specifications described in this RFC.

What is not yet done.

• Schema file.
  • migrations/mysql/1687512689_initialize_schema.{up|down}.sql are not complete form.
  • We were trying to integrate the schema of the tables into one file, but now the schemas have changed even more.
  • You should update the schema files.
• Sending notification process.
  • The function to send notifications has not yet been implemented.
  • Schema migration is a very powerful but risky feature, so user notification is necessary.

[cre8ivejp]

Closing this in favor of #812