Update nginx to 1.28.1-alpine3.23

Update nginx to 1.27.4-alpine3.21

Multi-platform build

Update libjwt & nginx version

Handle exp with fractional/invalid value

Update libjwt version

28 limit req zone with jwt embedded variables (#29)

* Add limit req in test image

* Extract variables in pre-access phase

Use nginx:1.24-alpine as base

Add auth_jwt_require directive

Embedded variables