allow for a registry mirror

[firefart]

docker supports registry-mirror only for Dockerhub images and not for other domains / registries. If you use a package mirror for other registries, you have to change the image name from ghcr.io/xxxx to registry-mirror/ghcr.io/xxxx. To avoid having to change the original docker-compose.yml or override it with a .override.yml file and keep the versions in sync, this change adds a REGISTRY_MIRROR_URL env variable to specify an optional registry mirror. If not defined it defaults to an empty string resulting in the original image name.

Example:

Without REGISTRY_MIRROR_URL:

ghcr.io/egos-tech/smtp:1.1.3

With REGISTRY_MIRROR_URL=internal.mirror.com/:

internal.mirror.com/ghcr.io/egos-tech/smtp:1.1.3

[Copilot]

Pull request overview

This PR adds support for using a registry mirror for Docker images by introducing a new REGISTRY_MIRROR_URL environment variable. This allows users to prepend a mirror URL to image names without modifying the docker-compose.yml file or managing override files.

Changes:

• Added REGISTRY_MIRROR_URL environment variable documentation in template.env
• Updated image references for all ghcr.io services (mail, misp-core, misp-modules, misp-guard) to use the optional registry mirror prefix

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
template.env	Adds documentation for the new REGISTRY_MIRROR_URL optional environment variable
docker-compose.yml	Updates four image references to support the registry mirror prefix using variable substitution with empty string default

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