JWT 解析器

解析 JWT Header、Payload、过期时间和常用声明，不做签名校验。

{
  "header": {
    "alg": "HS256",
    "typ": "JWT"
  },
  "payload": {
    "sub": "1001",
    "name": "RustPoint",
    "iat": 1710000000,
    "exp": 1710086400
  },
  "claims": {
    "algorithm": "HS256",
    "type": "JWT",
    "subject": "1001",
    "issuedAt": "2024-03-09T16:00:00.000Z",
    "expiresAt": "2024-03-10T16:00:00.000Z",
    "signatureLength": 9
  }
}