DI container cannot be built without valid JWT key

[alex-dev]

lcobucci/jwt@^4|^5 validate keys. Building DI container should be doable without any env var setup.

mercure:
  hubs:
    default:
      url: '%env(MERCURE_URL)%'
      public_url: '%env(MERCURE_PUBLIC_URL)%'
      jwt:
        secret: '%env(MERCURE_JWT_KEY)%'
        publish: ["*"]
        subscribe: ["*"]

Run php bin/console cache:warmup without providing MERCURE_JWT_KEY