Make exception API compatible with what Ruby expects

[jeremyevans]

Ruby expects that the first argument to Exception#initialize is a
string (or nil), since that is what Kernel#raise uses. Breaking that
assumption is a very bad idea.

This problem was introduced in 16be09a.
A backwards compatible approach would have added a response keyword
argument. Unfortunately, that ship has sailed, unless we want to break
backwards compatibility again.

Try to restore backwards compatibility and align with standard Ruby
exception behavior by checking whether the first message to #initialize
is an STMP::Response. If so, use it as the response. If not, treat it
as the exception message.

This prevents issues in code that does something like:

  raise exception_class, exception_message

Before this change, you'll get a NoMethodError later inside of
SMTPError#message, with no indication of the actual problem.

[bestwebua]

Good point 🥰 But also this library isn't following to the semvers standards too( Just look to this crazy adapter, which allows to tame minors versions: https://github.com/truemail-rb/truemail/blob/667888cbc4260db5a992a4a3f2612bc2b6882a5e/lib/truemail/validate/smtp/request.rb#L68 😀

[jeremyevans]

I think almost every Rubyist expects to be able to use Kernel#raise with two arguments, regardless of which exception class is used. Violating that expectation should not be done, even if doing so is technically considered allowable from a backwards compatibility standpoint due to sub 1.0 versioning.

[bestwebua]

Of course! Thanks for this catch. My comment was not about yours improvement. It's about this library, in general.

[tmtm]

👍