Use JWT_REFRESH_EXPIRATION_DELTA as refresh_token expiration delta

[alarrosa14]

I believe it makes sense to use JWT_REFRESH_EXPIRATION_DELTA setting as refresh_token expiration delta.

[ticosax]

please comment on the pull request directly to make them publicly visible in the conversation.

jpadilla#123

But I do not think it is a good idea to mix regular JWT settings with long refresh tokens. As the use-cases are different. If someone wants to use them both at the same time, you defeat the purpose of using long refresh tokens because you enforce re-login too often. Which is the purpose of long refresh tokens... not prompt the user for login.