Use Annotated to attach Field metadata rather than Fields as default values

[DiamondJoseph]

Now that the related Pydantic issue has been closed, we can follow through on this TODO and replace Field default arguments with annotated typehints for the dataclasses.

[coretl]

After a brief look I can't see the bit of pydantic docs that says you can put description in as a bare string, where did you find that bit of information?

[DiamondJoseph]

I was just naively doing it with the asumption that this was supported- think we likely need field: Annotated[type, Field(description="")], at which point any games in shortening each line are effectively eliminated. @callumforrester do you remember the motivation for the original TODO?

It does get us using defaults in a "more normal" way and having description on the field type rather than the default value

[callumforrester]

I suspect I just wanted to put it back how it was when we used vanilla dataclasses, before we adopted pydantic. The issue was resolved for v1 but may not have been for v2 (pydantic/pydantic#3496 (comment)).

[DiamondJoseph]

The PR that closed that issue was 9 days after the comment saying it was still an issue in Pydantic v2: I believe it is resolved for v2.

[coretl]

I see no reference in that PR of using bare strings in annotations...

[DiamondJoseph]

See above, think I jumped the gun and we need at least as much as field: Annotated[type, Field(description="")]