Support multiple databases connection reset

[heka1024]

What? Why?

• This PR support multiple databases connection reset
• In our company, we use multiple databases like below.

production:
  primary:
    database: my_primary_database
    username: root
    password: <%= ENV['ROOT_PASSWORD'] %>
    adapter: mysql2
  animals:
    database: my_animals_database
    username: animals_root
    password: <%= ENV['ANIMALS_ROOT_PASSWORD'] %>
    adapter: mysql2
    migrations_paths: db/animals_migrate

class AnimalsRecord < ApplicationRecord
  self.abstract_class = true

  connects_to database: { writing: :animals }
end

(Copied from https://guides.rubyonrails.org/active_record_multiple_databases.html)

We use basic Gruf::Interceptors::ActiveRecord::ConnectionReset but there was connection pool error. After some debug, we discovered that it was a problem about our non-primary database, AnimalsRecord in above example.

I think it's better to support this feature in upstream. So, I make a PR for it. 😄

How was it tested?

• My company uses it's hard-coded version (which replace target_classes to our ApplicationRecord's subclasses) in our production deployment.
• I made some test cases.

---

Thanks for this Gem. I love it ❤️

[splittingred]

This is great, thanks @heka1024 !

Let's get #181 merged in, then you can rebase, and we can merge from there.

[heka1024]

Thanks, @splittingred 😄 I rebase it with upstream!

[splittingred]

@heka1024 Great! Can you update CHANGELOG.md with a short description of the changes? Thanks!