📝 Docs: Schema Migrations with Alembic

[ryankwondev]

• Added a new section on how to use Alembic for schema migrations with SQLModel

I am aware that this document is still lacking in many aspects. I plan to further utilize the features of mkdocs to improve readability and add supplementary explanations to help users implement the steps appropriately in their respective environments.

Please let me know if there is any additional information that should be included. Going forward, I will actively contribute about the advanced usage of SQLModel in production environments.

[github-actions]

📝 Docs preview for commit a58a2c9 at: https://ddde98b2.sqlmodel.pages.dev

[ryankwondev]

FYI: It seems that the Linter is currently throwing errors for the tests in this PR, but this content does not directly involve the SQLModel code itself.

[ryankwondev]

@tiangolo Regarding the proposed roadmap, could you provide more details about your perspective on the direction for integrating migrations through Alembic?

#654 (comment)

[github-actions]

📝 Docs preview for commit e8077b9 at: https://8ffce397.sqlmodel.pages.dev

[m-mykytyn]

@ryankwondev
Thank you for the tutorial. It helped me a lot to understand the flow.
I have a suggestion for an enhancement:
Usually, the database connection string is set through environment variables and not directly through the alembic.ini file. It would be helpful to add this information as a chapter to the tutorial, as I have issues configuring SQLModel with Alembic for production usage.

[github-actions]

This pull request has a merge conflict that needs to be resolved.