fix: missing bad request generator

Add missing method NewBadRequestError

Add new Bad Request Error type

To improve our api handling this MR creates a BadRequestError that can be used to show that the client's error is malformed. Will allow us to then act on this error type by switching on our errors.

v0.3.1

• Added a README to the accounting package
• Fixed a bug with the Exchange function in the accounting package where it needs to return an error on sub zero exchange rates.

v0.3.0

• Added currency package for currency validation
• Added an accounting package for dealing with currency conversion and tax calculation

v0.2.1

• Fix bug resulting in no errors being thrown on malformatted auth tokens in grpc middleware

v0.2.0

Nullable types added in to deprecate old sqltypes

v0.1.1

• Pin now makes sure the wrapping error implements Unwrap() to re-surface the error that was wrapped.

v0.1.0

• Add the lusherr package
  • Provide Pin and Locate to attach caller information to determine where an error occurred in code
  • Provide standard errors to be used within domain logic for common exceptions e.g. Not Found, Database Query Error, Validation Error etc
• Extend lushauth package with auth policies
  • Add the concept of the Permitter interface to streamline permission checking for services
  • Add several base policies to be used and extended within domain logic of code bases e.g.:
    • MarketPolicy for market level access
    • RolePolicy for global role based access
    • UserPolicy for user specific access
    • GrantPolicy for action specific access
    • AllPolicy & AnyPolicy for combining access policies