Bump slf4j-api dependency to 2.x

[kamilkloch]

A mixture of 1.7 and 2.x breaks logging: https://www.slf4j.org/faq.html#changesInVersion200
(Logback 1.3+ already depends on slf4j-api 2.x).

[SethTisue]

not sure if this is a safe upgrade, or might be considered disruptive?

an example where it was considered disruptive: slick/slick#2542

[SethTisue]

@analytically @jxnu-liguobin @mox692 thoughts on how to proceed here?

I have no understanding of the issues involved, but: I think a typical solution in situations like this would be to roll one more patch release before taking the upgrade, for those who want a fix for #387 without any other implications, then take the SLF4J upgrade and publish again, with an appropriate version number bump...?

[mox692]

Yes, I agree.
It would be safer to separate the fixes for #387 and the update of the slf4j-api 2.x into different releases. Considering the example of Slick, upgrading to slf4j-api 2.x might require careful consideration.
I'll investigate a safe upgrade approach for scala-logging when I have time.