Caching of Issuers

[zbjornson]

Hello,

The Issuer constructor caches instances of itself:

https://github.com/panva/node-openid-client/blob/ba5869994ab67edeefbbd40af656e39021d1afa6/lib/issuer.js#L69

However, the cache is only ever used in the webfinger() method:

https://github.com/panva/node-openid-client/blob/ba5869994ab67edeefbbd40af656e39021d1afa6/lib/issuer.js#L123-L124

1. Is that the intended behavior?

2. Would you consider a way to disable caching? As currently written, caching in this LRU only wastes memory if we're not using webfinger(). Even if that is changed, we don't need caching because we store the issuer info in our database.

Thanks,
Zach