fix: Escape - in Regexp ranges

[ixti]

Bootsnap warns if it sees confusing regexp range like [a-b-_]. In general, it's better to escape dash in regexp ranges when it's supposed to mean literal dash.

This patch fixes warnings (when bootsnap is active):

/home/ixti/.gem/ruby/3.0.6/gems/lob-6.0.5/lib/openapi_client/models/bank_account.rb:260: warning: character class has '-' without escape
/home/ixti/.gem/ruby/3.0.6/gems/lob-6.0.5/lib/openapi_client/models/bank_account.rb:296: warning: character class has '-' without escape
/home/ixti/.gem/ruby/3.0.6/gems/lob-6.0.5/lib/openapi_client/models/bank_account.rb:395: warning: character class has '-' without escape
/home/ixti/.gem/ruby/3.0.6/gems/bootsnap-1.17.1/lib/bootsnap/compile_cache/iseq.rb:53: warning: character class has '-' without escape
/home/ixti/.gem/ruby/3.0.6/gems/bootsnap-1.17.1/lib/bootsnap/compile_cache/iseq.rb:53: warning: character class has '-' without escape
/home/ixti/.gem/ruby/3.0.6/gems/bootsnap-1.17.1/lib/bootsnap/compile_cache/iseq.rb:53: warning: character class has '-' without escape

Related-PR: #225

[ixti]

I would also recommend moving regexps into constants - there's no point in compiling them on every method call.

[mrkaspa]

I created this PR for solving the same #237

[ixti]

Yeah, we abandoned all hope with this gem - far too many issues with it and absolutely unresponsive devs:

• auto-generated code is rubbish
• no ruby-3.2, ruby-3.3 official support (or at least testing)

On top of that, Lob required us to upgrade the gem. The upgrade silently broke the code. Before the upgrade gem was correctly handling Tempfile passed as file: argument to Lob::LetterEditable (or whatever it was at that time). So we had code like:

Lob::LetterEditable.new({ file: tempfile, ... })

After the upgrade, the gem was seemingly working. No error, nothing. And we got billed for the letters that were sent. But the letters contained "#<File ...>" instead of the actual contents. The documentation says that file should be either PDF or HTML. One doesn't need to do quantum computing to clearly tell that #<File ...> is neither!

Lesson learned: don't use something created only to tick the box in the checklist of supported languages.