docs(example): implement OpenID Provider (#165)

* chore(example): implement OpenID Provider

* jwt profile and fixes

* some comments

* remove old op example

* fix code flow example

* add service user and update readme

* fix password for example use

* ignore example and mock folders for code coverage

* Update example/server/internal/storage.go

Co-authored-by: Silvan <silvan.reusser@gmail.com>

* Update client.go

Co-authored-by: Silvan <silvan.reusser@gmail.com>

example/server/internal/user.go

@@ -0,0 +1,24 @@
+package internal
+
+import (
+	"crypto/rsa"
+
+	"golang.org/x/text/language"
+)
+
+type User struct {
+	id                string
+	username          string
+	password          string
+	firstname         string
+	lastname          string
+	email             string
+	emailVerified     bool
+	phone             string
+	phoneVerified     bool
+	preferredLanguage language.Tag
+}
+
+type Service struct {
+	keys map[string]*rsa.PublicKey
+}