Allow _v1 suffix in Naming/VariableNumber without having to specify every individual method

[henrahmagix]

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

We've started suffixing some methods with _v1, _v2, etc. to indicate when we're effectively versioning them and introducing new versions, so we can do "soft" code releases where we start using the new method, and can still use the old method alongside to identify and upgrade existing things that were stored by the old method. E.g.

 def model_details_hasher(model)
+  NewHashingAlgorithm(model.to_json)
+end
+
+def model_details_hasher_v1(model)
   SomeHashingAlgorithm(model.to_s)
 end

We have Naming/VariableNumber set to EnforcedStyle: snake_case so the cop says it must be _v_1, _v_2, etc.

Describe the solution you'd like

We prefer _v1 to _v_1, so we'd like to be able to always allow these methods, whenever we add new ones. We also want to keep the rest of the rules under EnforcedStyle: snake_case the same.

Perhaps by allowing a regex to be configured, like AllowIf: /_v\d$/?

Or offering a specific option like AllowVersionSuffixInSnakeCase that does the same as the above, when the cop is set to EnforcedStyle: snake_case? This would be helpful if you want to control the speed of this feature (if allowing any regex could slow down rubocop and cause more bug reports/support issues as a result), and if other people would also want to use this combination of snake_case whilst allowing (imo) nicer-reading _v1.

Or even an option like MaxAllowedLettersBeforeNumber so you can also allow _a1, _b2, etc.

# .rubocop.yml
Naming/VariableNumber:
  EnforcedStyle: snake_case
  MaxAllowedLettersBeforeNumber: 1 # default is 0

Describe alternatives you've considered

Disable the cop inline on every method, which then feels like that particular method is "going against style", when it's actually the style we want.

Or add each new method name to the AllowedIdentifiers array on the cop settings, which will become tiresome as we use this method of code versioning more and more into the future.

# .rubocop.yml
Naming/VariableNumber:
  EnforcedStyle: snake_case
  AllowedIdentifiers:
    - model_details_hasher_v1