fix: allow required fields list to be specified as empty (openapi-generators#651)

The Pydantic model for OpenAPI schemas in this tool was more stringent about the required key than the OpenAPI / JSON Schema specs themselves, requiring a min_length of 1, when neither of those schemas actually do. This change just removes the min_length constraint on the required field, so that 'required: []' is allowed in inputs to this tool.

Author: benweint

Diff for: openapi_python_client/schema/openapi_schema_pydantic/schema.py

@@ -34,7 +34,7 @@ class Schema(BaseModel):
     uniqueItems: Optional[bool] = None
     maxProperties: Optional[int] = Field(default=None, ge=0)
     minProperties: Optional[int] = Field(default=None, ge=0)
-    required: Optional[List[str]] = Field(default=None, min_length=1)
+    required: Optional[List[str]] = Field(default=None)
     enum: Union[None, List[Any]] = Field(default=None, min_length=1)
     const: Union[None, StrictStr, StrictInt, StrictFloat, StrictBool] = None
     type: Union[DataType, List[DataType], None] = Field(default=None)