Add support for latest flower with celery 5

[jakemanger]

From version 1.0.1, Flower uses Celery 5 and has to be invoked in the same style as celery commands do.

This should let anyone cloning this project now to have it working correctly. If not, they will receive a

Docker – “flower”: executable file not found in $PATH: unknown

error

For more info, see: https://stackoverflow.com/questions/68267953/docker-flower-executable-file-not-found-in-path-unknown

[rasenx]

flower: image: mher/flower networks:

• ${TRAEFIK_PUBLIC_NETWORK?Variable not set}
• default env_file:
• .env environment:
• CELERY_BROKER_URL=amqp://guest@queue:5672//
• FLOWER_PORT=5555