feat: cache oidc.Provider to reduce pressure on OIDC identity provider (#47)

internal/proxy/director/layer/authn/oidc/layer.go

@@ -1,8 +1,13 @@
 package oidc
 
 import (
+	"time"
+
+	"forge.cadoles.com/cadoles/bouncer/internal/cache/memory"
+	"forge.cadoles.com/cadoles/bouncer/internal/cache/ttl"
 	"forge.cadoles.com/cadoles/bouncer/internal/proxy/director/layer/authn"
 	"forge.cadoles.com/cadoles/bouncer/internal/store"
+	"github.com/coreos/go-oidc/v3/oidc"
 	"github.com/gorilla/sessions"
 )
 
@@ -14,5 +19,10 @@ func NewLayer(store sessions.Store, funcs ...OptionFunc) *authn.Layer {
 		httpTransport:     opts.HTTPTransport,
 		httpClientTimeout: opts.HTTPClientTimeout,
 		store:             store,
+		oidcProviderCache: ttl.NewCache(
+			memory.NewCache[string, *oidc.Provider](),
+			memory.NewCache[string, time.Time](),
+			opts.OIDCProviderCacheTimeout,
+		),
 	}, opts.AuthnOptions...)
 }