Implement login resolver (#15)

* add sign_up_method to users table

* add session store

* implement login resolver

server/utils/urls.go

@@ -0,0 +1,16 @@
+package utils
+
+import (
+	"net/url"
+
+	"github.com/yauthdev/yauth/server/constants"
+)
+
+func GetFrontendHost() string {
+	u, err := url.Parse(constants.FRONTEND_URL)
+	if err != nil {
+		return `localhost`
+	}
+
+	return u.Hostname()
+}