Feat: add new --all-fields-required flag

[alythobani]

Fixes #1

Copied over from phillipdupuis#57:

Summary

Adds an --all-fields-required option (defaults to False) that ensures no generated TypeScript interface fields are marked as optional (fieldName?: ...), even if they have default values or default factories in the Pydantic models.

Motivation

Fields with defaults are viewed as optional by Pydantic, and thus currently become optional in the generated TypeScript interfaces.

This makes sense for API request schemas: clients don't need to provide values for these fields, since Pydantic can populate them with their defaults. However, for response schemas, the TS client should be able to know that these fields will be present, since Pydantic will populate them before sending the response data.

So, this new option (--all-fields-required) allows devs to represent response schemas without unnecessary optional markers (?) being added to fields that will always be present.

Approach

The implementation is nice and simple: at the end of each _clean_json_schema call, if --all-fields-required is set, we ensure every property name in schema["properties"] is included in schema["required"].

Note on required fields in Pydantic V1 vs V2

Under Pydantic V1, nullable fields were implicitly given default values of None, which the Pydantic docs mention here:

[!NOTE]
In Pydantic V1, fields annotated with Optional or Any would be given an implicit default of None even if no default was explicitly specified. This behavior has changed in Pydantic V2, and there are no longer any type annotations that will result in a field having an implicit default value.

But since --all-fields-required is just meant to mark every field as required whether or not it has a default or is nullable, our approach should be sound for either V1 or V2.