chore: rubocop

chore: fix api test conventions

chore: rubocop -A spec/

chore: more rubocop -A

fix failing test

rubocop fixes

removes helper methods that are in my opinion dead code

more rubocop fixes

rubocop -a --auto-gen-config

app/lib/bank_account_connector.rb

@@ -41,14 +41,14 @@ class BankAccountConnector
     end
   end
 
-  @@registered_classes = Set.new
+  @registered_classes = Set.new
 
   def self.register(klass)
-    @@registered_classes.add klass
+    @registered_classes.add klass
   end
 
   def self.find(iban)
-    @@registered_classes.each do |klass|
+    @registered_classes.each do |klass|
       return klass if klass.handles(iban)
     end
     nil