chore: Move Dockerfile at root to contrib/

In deployment docs https://backstage.io/docs/getting-started/deployment-other, we suggest doing a `yarn docker-build` and I thought the root Dockerfile was being used to build the image. Hence I modified it for some needs, but no changes were reflected. Later I found that `yarn docker-build` uses the `Dockerfile` present inside `packages/backend` https://github.com/backstage/backstage/blob/master/packages/backend/Dockerfile. So, I think the Dockerfile at the root is a bit misleading, and should be moved to contrib.

Signed-off-by: Himanshu Mishra <himanshu@orkohunter.net>

contrib/docker/frontend-with-nginx/Dockerfile

@@ -0,0 +1,20 @@
+FROM nginx:mainline
+
+# The purpose of this image is to serve the frontend app content separately.
+# By default the Backstage backend uses the app-backend plugin to serve the
+# app from the backend itself, but it may be desirable to move the frontend
+# content serving to a separate deployment, in which case this image can be used.
+
+# This dockerfile requires the app to be built on the host first, as it
+# simply copies in the build output into the image.
+
+# The safest way to build this image is to use `yarn docker-build:app`
+
+RUN apt-get update && apt-get -y install jq && rm -rf /var/lib/apt/lists/*
+
+COPY packages/app/dist /usr/share/nginx/html
+COPY docker/default.conf.template /etc/nginx/conf.d/default.conf.template
+COPY docker/run.sh /usr/local/bin/run.sh
+CMD run.sh
+
+ENV PORT 80

contrib/docker/frontend-with-nginx/docker/default.conf.template

@@ -0,0 +1,26 @@
+server {
+    listen       $PORT;
+    server_name  localhost;
+
+    #charset koi8-r;
+    #access_log  /var/log/nginx/host.access.log  main;
+
+    location / {
+        root   /usr/share/nginx/html;
+        index  index.html index.htm;
+        try_files $uri /index.html;
+    }
+
+    location /healthcheck {
+        return 204;
+    }
+
+    #error_page  404              /404.html;
+
+    # redirect server error pages to the static page /50x.html
+    #
+    error_page   500 502 503 504  /50x.html;
+    location = /50x.html {
+        root   /usr/share/nginx/html;
+    }
+}

contrib/docker/frontend-with-nginx/docker/run.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+
+set -Eeuo pipefail
+
+# Run nginx as root
+sed -i 's/user  nginx.*$//' /etc/nginx/nginx.conf
+
+# Write selected env vars to nginx config
+envsubst '$PORT' < /etc/nginx/conf.d/default.conf.template > /etc/nginx/conf.d/default.conf
+
+# Inject runtime config into the client
+function inject_config() {
+  # Read runtime config from env in the same way as the @backstage/config-loader package
+  local config
+  config="$(jq -n 'env |
+    with_entries(select(.key | startswith("APP_CONFIG_")) | .key |= sub("APP_CONFIG_"; "")) |
+    to_entries |
+    reduce .[] as $item (
+      {}; setpath($item.key | split("_"); $item.value | try fromjson catch $item.value)
+    )')"
+
+  >&2 echo "Runtime app config: $config"
+
+  local main_js
+  if ! main_js="$(grep -l __APP_INJECTED_RUNTIME_CONFIG__ /usr/share/nginx/html/static/*.js)"; then
+    echo "Runtime config already written"
+    return
+  fi
+  echo "Writing runtime config to ${main_js}"
+
+  # escape ' and " twice, for both sed and json
+  local config_escaped_1
+  config_escaped_1="$(echo "$config" | jq -cM . | sed -e 's/[\\"\x27]/\\&/g')" # \x27 = '
+  # escape / and & for sed
+  local config_escaped_2
+  config_escaped_2="$(echo "$config_escaped_1" | sed -e 's/[\/&]/\\&/g')"
+
+  # Replace __APP_INJECTED_RUNTIME_CONFIG__ in the main chunk with the runtime config
+  sed -e "s/__APP_INJECTED_RUNTIME_CONFIG__/$config_escaped_2/" -i "$main_js"
+}
+
+inject_config
+
+exec nginx -g 'daemon off;'