1.31.0
(feat): Add support for SDK variables (x-fern-sdk-variables / variables in api.yml).
Each variable is exposed as an optional keyword on the root client (e.g.
Client.new(target_account_sid: "AC...")); path parameters bound to a variable are
removed from the endpoint methods and request classes, and the value is read from
the client instead. String variables declared with an env fall back to
ENV.fetch("<ENV_VAR>", nil) when the keyword is omitted, and endpoints raise an
ArgumentError with a clear message when a required variable is still unset.