fix for #38:

        # Replace '/' with '-' and check for any invalid characters

        APP_VERSION=$(echo "$CI_COMMIT_REF_NAME" | sed 's|/|-|g')

        # Check for invalid characters (only allow lowercase letters, digits, '_', '.', '-')

        # Check for invalid characters (only allow lowercase and uppercase letters, digits, '_', '.', '-')

        if echo "$APP_VERSION" | grep -q '[^a-zA-Z0-9._-]'; then

          echo "Error: Branch name contains invalid characters for Docker tags. Only a-z, 0-9, '_', '.', and '-' are allowed."

          echo "Error: Branch name contains invalid characters for Docker tags. Only a-z, A-Z, 0-9, '_', '.', and '-' are allowed."

          exit 1

        fi

        # Convert to lowercase

        export APP_VERSION=$(echo "$APP_VERSION" | tr 'A-Z' 'a-z')

        export APP_VERSION

      fi

    - echo "APP_VERSION set to $APP_VERSION"