Frontend url configuration is overwritten by addon entrypoint

[mik-laj]

Description of the issue

Hello,

I would like to have links in Z2M on the device details screen. Similar to what WLED integration provides:
("VISIT" button)

On the HA side, to do this, we need to set the configuration_url field in MQTT config. It is covered by: https://www.home-assistant.io/integrations/mqtt/
Zigbee2mqtt implements the appropriate code that sets this field.
https://github.com/Koenkk/zigbee2mqtt/blob/902db5ea5b12ddf7053faae32df4b6b4c48f269b/lib/extension/homeassistant.ts#L1962-L1983
This requires the frontend/url config to be set.
Unfortunately, this addon overwrites the entire frontend section configuration.

hassio-zigbee2mqtt/common/rootfs/docker-entrypoint.sh

Line 70 in f8e493f

export ZIGBEE2MQTT_CONFIG_FRONTEND='{"enabled":true,"port": 8099}'

Environment variables have higher priority than the configuration file:
https://github.com/Koenkk/zigbee2mqtt/blob/master/lib/util/settings.ts#L387-L388

And if we configure an entire section, all section options are overwritten.
https://github.com/Koenkk/zigbee2mqtt/blob/902db5ea5b12ddf7053faae32df4b6b4c48f269b/lib/util/settings.ts#L459-L465

It would be great if the extension automatically set the frontend/url value, or at least allowed overriding the value in the configuration file.

Best regards,
Kamil Breguła

Addon version

1.42.0-2

Platform

N/A

Logs of the issue (if applicable)

No response