Implement `InvalidRequestError`

[codebestia]

Description

Raised on HTTP 400/422 responses — malformed parameters, missing required fields, or out-of-range values. Should expose field-level validation details from the API so the developer knows which parameter is wrong.

Proposed Steps

• Define InvalidRequestError(ShadeError) in errors.py.
• Add param: Optional[str] (the offending field name) and field_errors: dict (all field errors from API response).
• Populate from API error response format, e.g. {"error": {"code": "invalid_param", "param": "amount", "message": "..."}}.

Acceptance Criteria

• A 400 response raises InvalidRequestError.
• error.param names the offending field when the API provides one.
• error.field_errors contains all field-level errors from the API response.
• str(error) includes the param name in the message.

[samueloyibodevv]

Hi! I’d love to contribute to this issue. It looks interesting and I’d be happy to take it on if it’s still available.