Allow injecting validation errors

[DanielSchaffer]

• refactor metadata.model.builder to collect all validation errors as a data structure instead of throw an error
• add single error class containing all errors
• update ModelBuilder APIs to include overrides:
  • current API signature
  • throwOnValidationError: false in MemberBuilderOptions returns Error instance or model type
  • e.g. constructModel<TModel, TOptions extends NoThrowOnValidationErrorOptions>(type: Constructor<TModel>, source: any, options: TOptions): Error | TModel
• add @HandleModelErrors() decorator that allows decorated routes to process requests with invalid input data (request body, query param, or path param); inject original source value for each failing provider
• add @RequestModelErrors() injectable decorator that injects map of errors collected for any injected param
• throw an error from the decorators if @RequestModelErrors is used without @HandleModelErrors or vice-versa