[alex-leb]

enforces_api_version and requires_api_version looked each method up with instance_method as soon as they ran, so declaring them at the top of a class, before the methods, raised NameError and broke the specs. This lets the declarations sit at the top of the class.

Change

• Each declaration now prepends a small ApiVersionChecker::Check module whose methods run the version check and then call the class's own method through super. The class methods don't have to exist yet, so the declaration works before or after them. Arguments, keyword arguments and blocks are passed through as before.
• The enforces_api_version declarations in the 8 wrapper classes (AccountWebhooks, AnalyticsTags, ApiKeys, DomainKeys, Domains, MailingLists, Routes, Webhooks) move to the top, right after include ApiVersionChecker.

Guarding against typos

Declaring before the methods means a misspelled name no longer fails when the class loads; it would just leave the intended method unchecked. Check records the names it wraps, and a new spec loads every class that includes the checker and fails if any declared name isn't defined in that class. With :mtach added to the Routes declaration, it fails with Mailgun::Routes#mtach.

Testing

• Helper spec: 3 new examples for declarations placed before the methods, plus the guard; 24 examples, 0 failures.
• Full suite, run without credentials: 423 examples, 0 failures; line coverage 96.39%; RuboCop clean.
• The guard loads only the classes that include the checker. Loading the whole gem would pull in the legacy Mailgun::Tags class, which no spec covers (25% line coverage), and drop the suite below the 95% coverage minimum.