Add new Rails/FreezeTime cop

[ydah]

Refs: https://github.com/rubocop/rails-style-guide#freeze_time

This cop Identifies usages of travel_to with argument current time and
change them to use freeze_time instead.

@example

# bad
travel_to(Time.now)
travel_to(DateTime.now)
travel_to(Time.current)
travel_to(Time.zone.now)
travel_to(Time.now.in_time_zone)
travel_to(Time.current.to_time)

# good
freeze_time

---

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• [-] Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.
• If this is a new cop, consider making a corresponding update to the Rails Style Guide.

[koic]

If this is a new cop, consider making a corresponding update to the Rails Style Guide.

Can you open it to the Rails Style Guide first?

[ydah]

The freeze_time description mentioned in this PR has been merged into the Rails Style Guide.
Sorry for the back and forth.

https://github.com/rubocop/rails-style-guide#freeze_time

[nekonenene]

Even if we adopt this pull request, I thought it would be appropriate to merge it into https://github.com/rubocop/rubocop-rspec .

[koic]

Even if we adopt this pull request, I thought it would be appropriate to merge it into https://github.com/rubocop/rubocop-rspec .

The testing framework provided by Rails core is ActiveSupport::TestCase based on Minitest. Not RSpec. travel_to and freeze_time methods are provided by ActiveSupport, so this cop would be better placed in this rubocop-rails.

[nekonenene]

I see. I made a mistake because it is related to the test, but you're right!

[koic]

Thanks!