Throw exception when using classes from other JSON libraries with Gson #435

	# This workflow makes sure that a pull request does not make any incompatible changes
	# to the public API of Gson
	name: Check API compatibility

	on: pull_request

	jobs:
	check-api-compatibility:
	runs-on: ubuntu-latest

	steps:
	- name: Checkout old version
	uses: actions/checkout@v3
	with:
	ref: ${{ github.event.pull_request.base.sha }}
	path: 'gson-old-japicmp'

	- name: Set up JDK 11
	uses: actions/setup-java@v3
	with:
	distribution: 'temurin'
	java-version: '11'
	cache: 'maven'

	- name: Build old version
	run: \|
	cd gson-old-japicmp
	# Set dummy version
	mvn --batch-mode --no-transfer-progress org.codehaus.mojo:versions-maven-plugin:2.11.0:set -DnewVersion=JAPICMP-OLD
	# Install artifacts with dummy version in local repository; used later by Maven plugin for comparison
	mvn --batch-mode --no-transfer-progress install -DskipTests

	- name: Checkout new version
	uses: actions/checkout@v3

	- name: Check API compatibility
	id: check-compatibility
	run: \|
	mvn --batch-mode --fail-at-end --no-transfer-progress package japicmp:cmp -DskipTests

	- name: Upload API differences artifacts
	uses: actions/upload-artifact@v3
	# Run on workflow success (in that case differences report might include added methods and classes)
	# or when API compatibility check failed
	if: success() \|\| ( failure() && steps.check-compatibility.outcome == 'failure' )
	with:
	name: api-differences
	path: \|
	**/japicmp/default-cli.html
	**/japicmp/default-cli.diff
	# Plugin should always have created report files (though they might be empty)
	if-no-files-found: error

Provide feedback