Return consistent result using '[]' and accessor methods of Stripe::StripeObject class

[doom-weaver]

Is your feature request related to a problem? Please describe.

Presently, using [] or an accessor on a StripeObject return different results:

 irb(main):005> require('stripe')
 => true
 irb(main):006> x = Stripe::StripeObject.new()
 => 
#<Stripe::StripeObject:0x13088> JSON: {
...
 irb(main):007> x.a
 /Users/cleve/.asdf/installs/ruby/3.1.4/lib/ruby/gems/3.1.0/gems/stripe-5.55.0/lib/stripe/stripe_object.rb:399:in `method_missing': undefined method `a' for #<Stripe::StripeObject:0x13088> JSON: { (NoMethodError)
}
        from (irb):7:in `<main>'
        from /Users/cleve/.asdf/installs/ruby/3.1.4/lib/ruby/gems/3.1.0/gems/irb-1.9.0/exe/irb:9:in `<top (required)>'
        from /Users/cleve/.asdf/installs/ruby/3.1.4/bin/irb:25:in `load'
        from /Users/cleve/.asdf/installs/ruby/3.1.4/bin/irb:25:in `<main>'
 irb(main):008> x["a"]
 => nil
 irb(main):009> 

Using the accessor raises a NoMethodError while the use of the [] method returns nil.

Describe the solution you'd like

Have both accessor patterns generate the same output for non-existent fields. This would be more consistent semantically.

Describe alternatives you've considered

It is easy to work around this using [] or the accessor depending on the context.

Additional context

In my case I am using the metadata field of stripe payment intent to control some operational metrics and backend processes. Hence - we need to check metadata fields to determine what action, if any, to take and what metrics to report. That is when this difference was encountered.

I could not find documentation for the fact that the accessor raises errors while the hash does not - short of updating the library documenting the difference in the Stripe Ruby docs would be a nice win.

[pakrym-stripe]

I've documented the behavior in #1339. I'll keep the issue open to see if we get other reports of inconsistency being confusing.