Document using SQLAlchemy column types; add pydantic.EmailStr support

[rmasters]

When I start a new project, I typically start with a User model and always bump into this error:

ValueError: <class 'pydantic.networks.EmailStr'> has no matching SQLAlchemy type

Today I decided to dig into this, and found that EmailStr doesn't subclass str, which explains why it needs a Field(sa_type=String()). I noticed the AutoString types for ipaddress & pathlib, and figured EmailStr might be popular enough to be worth adding (example discussion).

As part of this, in order to test that change I've started documenting how SA column types work in SQLModel. I also noticed the mention about varchar length and documented that too.

Let me know if you'd prefer this as two separate PRs and I can cherry-pick it out - they're only together as I wanted to use the docs-tutorial tests (which are awesome!)

---

• [x] Add pydantic.EmailStr support to get_sqlalchemy_type
• [x] Add documentation for column types, including varchar/text string lengths
• [ ] ~Finish testing "exotic sqlalchemy type" (geoalchemy2) tests~
  • I originally had some test cases for GIS using geoalchemy2's SQLAlchemy column types. Testing this with sqlite requires libspatialite, which probably needs some CI work/containerization to add this to the environment. I'll revisit this as a separate advanced tutorial in another PR if there's interest.
• [x] Finish testing ipaddress, pathlib & EmailStr AutoString type alises
• [ ] Rebase commits to a clean history

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[mockingjet]

Any update on this MR?