feat: add caching for terragrunt

enable terragrunt provider caching, when inputs.cache-dependencies is
set

Author: norman-zon

action.yml

@@ -309,6 +309,8 @@ runs:
         NO_BACKEND: ${{ inputs.no-backend }}
         DEBUG: 'true'
         TF_PLUGIN_CACHE_DIR: ${{ github.workspace }}/cache
+        TERRAGRUNT_PROVIDER_CACHE:  ${{ inputs.cache-dependencies == 'true' && "1" || "0" }}
+        TERRAGRUNT_PROVIDER_CACHE_DIR: ${{ github.workspace }}/cache
       run: |
           cd $GITHUB_ACTION_PATH/cli
           go build -o digger ./cmd/digger
@@ -336,6 +338,9 @@ runs:
         INPUT_DIGGER_COMMAND: ${{ inputs.command }}
         INPUT_DRIFT_DETECTION_SLACK_NOTIFICATION_URL: ${{ inputs.drift-detection-slack-notification-url }}
         NO_BACKEND: ${{ inputs.no-backend }}
+        TF_PLUGIN_CACHE_DIR: ${{ github.workspace }}/cache
+        TERRAGRUNT_PROVIDER_CACHE:  ${{ inputs.cache-dependencies == 'true' && "1" || "0" }}
+        TERRAGRUNT_PROVIDER_CACHE_DIR: ${{ github.workspace }}/cache
       id: digger
       shell: bash
       run: |
@@ -347,10 +352,12 @@ runs:
 
     - uses: actions/cache/save@v4
       name: cache-save
+      if: ${{ inputs.cache-dependencies == 'true' }}
       with:
         path: ${{ github.workspace }}/cache
         key: digger-cache-${{ hashFiles('**/cache') }}
-      if: ${{ inputs.cache-dependencies == 'true' }}
+        restore-keys: |
+          digger-cache-
 
 branding:
   icon: globe