Transition from dgrijalva/jwt-go pkg to golang-jwt/jwt

`jwt-go` has a security vulnerability (CVE-2020-26160). There is no patch available and users of `jwt-go` are advised to migrate to `golang-jwt` at version 3.2.1. 👀

Start by locating the repository's jwt-go dependency and imports, then review how the package is used. Migrate those references to golang-jwt/jwt at version 3.2.1 and run the existing test suite to confirm configuration loading still works without the vulnerable dependency.

Written by the indexing model from the issue text.