Align code with Drupal standards and add GitLab CI for automated checks

Problem/Motivation

Some code standard issues have been detected in this module across multiple files. It is recommended to apply the necessary changes to align the code with Drupal's coding standards. This will improve maintainability, readability, and overall adherence to best practices.
Additionally, it's recommended to add a .gitlab-ci.yml file to enable continuous integration (CI) jobs that automatically check coding standards and help maintain code quality over time.

Steps to reproduce

Download the module and place it in the modules/custom directory.

Run phpcs with Drupal coding standards on the module directory.

Observe the reported coding standard violations in the output.

Proposed resolution

Review all code files in the module and resolve the detected coding standard issues.

Use automated tools like phpcbf where applicable and manually fix violations not covered by the tool.

Ensure the module complies fully with Drupal coding standards (phpcs shows no violations).

Add a .gitlab-ci.yml file to run automated checks using phpcs on every commit or merge request.

Remaining tasks

Run phpcs to identify the violations.

Fix the issues using phpcbf and manual adjustments.

Re-run phpcs to confirm resolution.

Add and configure .gitlab-ci.yml with a job that runs phpcs.

Review the changes through a merge request.

Test the module to ensure no regressions.

User interface changes

No user interface changes are expected. This issue is related only to code quality and standards compliance.

API changes

No API changes are expected.

Data model changes

No changes to the data model are anticipated.