docs(proxy): Clarify PROXY_OIDC_USERINFO_CACHE_TTL value

Try to make it more precise when that value is actually relevant.

Closes: #2252

Author: rhafer

services/proxy/pkg/config/config.go

@@ -134,7 +134,7 @@ type Cache struct {
 	Nodes              []string      `yaml:"addresses" env:"OC_CACHE_STORE_NODES;PROXY_OIDC_USERINFO_CACHE_STORE_NODES" desc:"A list of nodes to access the configured store. This has no effect when 'memory' store is configured. Note that the behaviour how nodes are used is dependent on the library of the configured store. See the Environment Variable Types description for more details." introductionVersion:"1.0.0"`
 	Database           string        `yaml:"database" env:"OC_CACHE_DATABASE" desc:"The database name the configured store should use." introductionVersion:"1.0.0"`
 	Table              string        `yaml:"table" env:"PROXY_OIDC_USERINFO_CACHE_TABLE" desc:"The database table the store should use." introductionVersion:"1.0.0"`
-	TTL                time.Duration `yaml:"ttl" env:"OC_CACHE_TTL;PROXY_OIDC_USERINFO_CACHE_TTL" desc:"Default time to live for user info in the user info cache. Only applied when access tokens has no expiration. See the Environment Variable Types description for more details." introductionVersion:"1.0.0"`
+	TTL                time.Duration `yaml:"ttl" env:"OC_CACHE_TTL;PROXY_OIDC_USERINFO_CACHE_TTL" desc:"Default time to live for user info in the user info cache. This value is only applied when the token expiration cannot be extracted from the access tokens (e.g. when non-JWT access tokes are used). See the Environment Variable Types description for more details." introductionVersion:"1.0.0"`
 	DisablePersistence bool          `yaml:"disable_persistence" env:"OC_CACHE_DISABLE_PERSISTENCE;PROXY_OIDC_USERINFO_CACHE_DISABLE_PERSISTENCE" desc:"Disables persistence of the cache. Only applies when store type 'nats-js-kv' is configured. Defaults to false." introductionVersion:"1.0.0"`
 	AuthUsername       string        `yaml:"username" env:"OC_CACHE_AUTH_USERNAME;PROXY_OIDC_USERINFO_CACHE_AUTH_USERNAME" desc:"The username to authenticate with the cache. Only applies when store type 'nats-js-kv' is configured." introductionVersion:"1.0.0"`
 	AuthPassword       string        `yaml:"password" env:"OC_CACHE_AUTH_PASSWORD;PROXY_OIDC_USERINFO_CACHE_AUTH_PASSWORD" desc:"The password to authenticate with the cache. Only applies when store type 'nats-js-kv' is configured." introductionVersion:"1.0.0"`