Added support for redis expire keys

[katorres02]

CINT Oauth2 authentication flow does not use a refresh_token logic - instead they expect the clients to request a new authorization token when is expired.

This was validated with the CINT official documentation and the response from the authorization endpoint.

For this particular case we need to add expiration support for tokens stored using this library.
- Added expires_in argument to the constructor - This is an optional value
- Added default value to expires_in - default value nil
- The expires time will be only added to the key if the argument is present - otherwise it will use the default expiration time
- This change does not break previous implementations

⚠️ After some more thoughts we decided to use a different approach for refreshing the token for CINT
What is left in this PR are the gem updates and a couple rubocop fixes

[loto]

Good job 👍

[jeromepl]

Isn't it weird that the redis.set call is not inside the lock! block? This feels like a bug of the gem 🤔 It looks like it should be

Suggested change

	value = lock!(&block)
	redis.set(key, value)
	store_value!(value)
	lock! do
	value = block.call
	store_value!(value)
	end

Otherwise, I think it would be technically possible that a process that started later than another ends up storing its value in Redis first, so it would be overwritten by the first process.

[katorres02]

Agree, good catch

[VitorGultzgoff]

Nice!