Forge promotions and maven repo URLs are configurable (#3587)

Dockerfile

@@ -48,7 +48,7 @@ RUN easy-add --var os=${TARGETOS} --var arch=${TARGETARCH}${TARGETVARIANT} \
   --var version=${MC_SERVER_RUNNER_VERSION} --var app=mc-server-runner --file {{.app}} \
   --from ${GITHUB_BASEURL}/itzg/{{.app}}/releases/download/{{.version}}/{{.app}}_{{.version}}_{{.os}}_{{.arch}}.tar.gz
 
-ARG MC_HELPER_VERSION=1.48.1
+ARG MC_HELPER_VERSION=1.48.2
 ARG MC_HELPER_BASE_URL=${GITHUB_BASEURL}/itzg/mc-image-helper/releases/download/${MC_HELPER_VERSION}
 # used for cache busting local copy of mc-image-helper
 ARG MC_HELPER_REV=1

docs/types-and-platforms/server-types/forge.md

@@ -45,6 +45,11 @@ In both of the cases above, there is no need for the `VERSION` or `FORGE_VERSION
 
     If an error occurred while installing Forge, it might be possible to resolve by temporarily setting `FORGE_FORCE_REINSTALL` to "true". Be sure to remove that variable after successfully starting the server.
 
+URLs configurable via environment variables:
+
+- `FORGE_PROMOTIONS_URL`: default is https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json
+- `FORGE_MAVEN_REPO_URL`: default is https://maven.minecraftforge.net
+
 ## Alternatives
 
 ### NeoForge