Use boolean values instead of pointers

[AlexanderYastrebov]

Signed-off-by: Alexander Yastrebov alexander.yastrebov@zalando.de

[AlexanderYastrebov]

Similar to #18 this change gets rid of primitive value pointers making it simpler to use struct literals to define options.

[MicahParks]

This does change the behavior of Options, as false is the default bool value and is a valid Options field value.

(0 can represent an uninitialized time.Duration because it's an invalid Options field value.)

It could be a breaking change if someone passed in multiple options through the variadic arguments with the first one being a pointer to true and the second one being unspecified.

However, I could change the function comment to note that.

I'll consider this while I'm AFK. And likely run the tests, linters, and accept the PR when I get the chance.

[AlexanderYastrebov]

It could be a breaking change

By default both flags are false in JWKs. This would be a breaking change if one used multiple options and former option set the flag while the latter reset (i.e. end result is false) like:

	t := true
	f := false
	jwks, err := keyfunc.Get(jwksURL, keyfunc.Options{RefreshUnknownKID: &t}, keyfunc.Options{RefreshUnknownKID: &f})