feat: make cache key consistent (and configurable) (#38)

.github/workflows/integration.yaml

@@ -41,6 +41,12 @@ on:
         default: ../../../vendor/bin/phpunit
         description: "The integration test command to run"
 
+      composer_cache_key:
+        type: string
+        required: false
+        default: ''
+        description: A key to version the composer cache. Can be incremented if you need to bust the cache.
+
     secrets:
       composer_auth:
         required: false
@@ -117,7 +123,7 @@ jobs:
     - name: "Cache Composer Packages"
       uses: actions/cache@v3
       with:
-        key: 'composer | v3 | "$(Agent.OS)"  | composer.lock | ${{ matrix.composer }} | ${{ matrix.php }} | ${{ matrix.magento }}' 
+        key: "composer | v4 | ${{ inputs.composer_cache_key }} | ${{ hashFiles('composer.lock') }} | ${{ matrix.os }} | ${{ matrix.composer }} | ${{ matrix.php }} | ${{ matrix.magento }}"
         path: ${{ steps.composer-cache.outputs.dir }}
 
     - run: composer config repositories.local path ${{ inputs.source_folder }}