Consider throwing an error immediately in `verifyTransaction` instead of returning a list of messages

[davidyuk]

Pros

• won't be necessary to try/catch api calls in specific validations
• simpler outer interface
• better stacktrace

Cons

• not able to show all errors, only the first one

Alternatively, it can return a special error (MultipleError or AggregateError?), containing a list of validation errors