Add Composer cache step to GitHub workflow

This commit introduces caching for Composer dependencies in the CI workflow using `actions/cache@v4`. It optimizes build times by reusing dependencies across runs, keyed by the `composer.lock` file hash. Removed unused dependency matrix from the PHP job matrix configuration.

.github/workflows/integrate.yml

@@ -58,9 +58,6 @@ jobs:
           - "8.2"
           - "8.3"
           - "8.4"
-        dependencies:
-          - "lowest"
-          - "highest"
     runs-on: ${{ matrix.operating-system }}
     steps:
       - name: "Set up PHP"
@@ -76,6 +73,14 @@ jobs:
         with:
           fetch-depth: 0
 
+      - name: "Cache Composer dependencies"
+      - uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
       - name: "Install dependencies"
         uses: "ramsey/composer-install@v3"
         with:
@@ -111,6 +116,14 @@ jobs:
         with:
           fetch-depth: 0
 
+      - name: "Cache Composer dependencies"
+      - uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
       - name: "Install dependencies"
         uses: "ramsey/composer-install@v3"
         with:
@@ -138,6 +151,14 @@ jobs:
       - name: "Checkout code"
         uses: "actions/checkout@v4"
 
+      - name: "Cache Composer dependencies"
+      - uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
       - name: "Validate Composer configuration"
         run: "composer validate"
 
@@ -171,6 +192,14 @@ jobs:
       - name: "Checkout code"
         uses: "actions/checkout@v4"
 
+      - name: "Cache Composer dependencies"
+      - uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
       - name: "Get tags"
         run: git fetch --tags origin
 
@@ -207,6 +236,14 @@ jobs:
       - name: "Checkout code"
         uses: "actions/checkout@v4"
 
+      - name: "Cache Composer dependencies"
+      - uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
       - name: "Fetch Git base reference"
         run: "git fetch --depth=1 origin ${GITHUB_BASE_REF}"
 
@@ -229,6 +266,14 @@ jobs:
       - name: "Checkout code"
         uses: "actions/checkout@v4"
 
+      - name: "Cache Composer dependencies"
+      - uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-composer-
+
       - name: "Check exported files"
         run: |
           EXPECTED="LICENSE,README.md,RELEASES.md,SECURITY.md,composer.json,link,package.json"