Implement ExtractType cop

[0legovich]

@DmitryTsepelev Added cop GraphQL/ExtractType.
Closes #5

[DmitryTsepelev]

Hi @0legovich, thanks for the contribution, great job! I've added some comments and ideas and please add yourself to the Changelog (right after the ## master line)

[0legovich]

@DmitryTsepelev Hi. Thank you for your quick feedback.
I updated the PR according to the comments.

[DmitryTsepelev]

LGTM! I tried to run the cop in the real–world project and realized that my initial requirements were not full. In some cases we don't need to extract the type, for instance, some teams name Boolean fields starting with is_, and of course when there are more then two fields gem suggests to extract the new type Is.

Solution should be simple: we can add one more config option called Prefixes and skip the check for listed prefixes (example from rubocop-rspec). I guess defaults could be is, avg, min, max.

However, the initial task is definitely completed, please let me know if you want to face this last challenge, or we can call it a day and handle it later 🙂

[0legovich]

I think I will add the Prefixes parameter and its processing within the current PR, as a separate commit.

[0legovich]

@DmitryTsepelev I also thought about composite prefixes.
For example:

field :contact_info_phone, String, null: false
field :contact_info_name, String, null: false

Here the composite prefix is contact_info.
Do you think we should handle such cases?

[DmitryTsepelev]

Yeah, it would be really helpful to handle such cases too, good catch

[0legovich]

@DmitryTsepelev Now we are able to recognize composite prefixes. What do you think about this implementation?

[DmitryTsepelev]

LGTM! I'm going to merge it right now and make some minor tweaks in the master branch, thank you for the hard work!