Add GH Actions workflow to publish container image to GHCR (#1158) #1

	name: Build Docker Image, Push to GHCR

	on:
	push:
	# Publish HEAD of main branch as :latest image tag
	branches: [ "main" ]
	# Publish semver tags as named image tags
	tags: [ 'v..*' ]

	env:
	REGISTRY: ghcr.io
	IMAGE_NAME: maproulette/maproulette-backend

	jobs:
	build:
	runs-on: ubuntu-latest
	steps:
	- name: Checkout repository
	uses: actions/checkout@v4

	# Set up BuildKit Docker container builder to be able to build
	# multi-platform images and export cache
	# https://github.com/docker/setup-buildx-action
	- name: Set up Docker Buildx
	uses: docker/setup-buildx-action@v3

	# Login to Docker registry
	# https://github.com/docker/login-action
	- name: Log into registry ${{ env.REGISTRY }}
	uses: docker/login-action@v3
	with:
	registry: ${{ env.REGISTRY }}
	username: ${{ github.actor }}
	password: ${{ secrets.GITHUB_TOKEN }}

	# Extract metadata (tags, labels) for Docker
	# https://github.com/docker/metadata-action
	- name: Extract Docker metadata
	id: meta
	uses: docker/metadata-action@v5
	with:
	images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
	tags: \|
	type=ref,event=branch
	type=semver,pattern={{version}}
	type=semver,pattern={{major}}.{{minor}}
	type=semver,pattern={{major}}

	# Build and push Docker image with Buildx
	# https://github.com/docker/build-push-action
	- name: Build and push Docker image
	id: build-and-push
	uses: docker/build-push-action@v5
	with:
	context: .
	push: true
	tags: ${{ steps.meta.outputs.tags }}
	labels: ${{ steps.meta.outputs.labels }}
	cache-from: type=gha
	cache-to: type=gha,mode=max

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