use ssh key instead of pat

Author: 0marperez

.github/actions/merge-main/action.yml

@@ -7,15 +7,21 @@ inputs:
 runs:
   using: composite
   steps:
-    - name: Merge Main
+    - name: Checkout repository
       uses: actions/checkout@v4
       with:
         fetch-depth: 0
-        token: ${{ secrets.CI_USER_PAT }}
-    - run: |
+        ssh-key: ${{ secrets.CI_USER_SSH_KEY }}
+
+    - name: Set up Git
+      shell: bash
+      run: |
         git config user.name aws-sdk-kotlin-ci
         git config user.email "[email protected]"
 
+    - name: Run Script
+      shell: bash
+      run: |
         input=${{ inputs.exempt-branches }}
 
         function fetch_latest_changes() {