feat: schema migration

[TimoKramer]

SUMMARY

• schema migration as norm namespace in datahike.
• github discussion: https://github.com/replikativ/datahike/discussions/582
• fixes #13
• relates to #532

Checks

Feature

• [x] Implements an existing feature request. Make sure the feature request has been accepted for implementation before opening a PR.
• [x] Related issues linked using fixes #number
• [x] Documentation added
• [x] Formatting checked

[TimoKramer]

@fpischedda I am thinking since you wished for a way to avoid conflicting schema migrations with colleagues that we could have something like a tool that tracks the migrations in a separate file. Then you would get merge conflicts in case you didn't rebase the last commit to this tracking file. @kordano came up with the idea, there is a tool called atlas for sql-dbs that does this already.

[fpischedda]

Hi @TimoKramer

This is a neat idea! I will also have a look at atlas, it could be useful at $work, thanks @kordano for mentioning it 🙂

[jsmassa]

I think there is something missing in the documentation that describes in which cases it makes sense to use norms for schema migration. For someone that hasn't read the conversation in this issue it doesn't become quite clear why you would need to have norms installed for something that would need to be done only once, naively assuming you only have one database of a kind.