docs: detailed SonarQube configuration instructions (with SonarCloud requirements)

### `mvn-sonar` job — SonarQube analysis

This job is **disabled by default** and performs a SonarQube analysis of your code.

The job is bound to the `test` stage and uses the following variables:

This job, **disabled by default**, is bound to the `test` stage and performs a SonarQube analysis of your code.

This job uses the following variables:

| Name                     | description                            | default value     |

| ------------------------ | -------------------------------------- | ----------------- |

| `SONAR_HOST_URL`         | SonarQube server url                   | _none_ (disabled) |

| :lock: `SONAR_TOKEN`     | SonarQube authentication [token](https://docs.sonarqube.org/latest/user-guide/user-token/) (depends on your authentication method) | _none_ |

| :lock: `SONAR_LOGIN`     | SonarQube login (depends on your authentication method)                | _none_ |

| :lock: `SONAR_TOKEN`     | SonarQube authentication [token](https://docs.sonarsource.com/sonarqube/latest/user-guide/user-account/generating-and-using-tokens/#using-a-token) (depends on your authentication method) | _none_ |

| :lock: `SONAR_LOGIN`     | SonarQube [login](https://docs.sonarsource.com/sonarqube/latest/extension-guide/web-api/#http-basic-access) (depends on your authentication method)                | _none_ |

| :lock: `SONAR_PASSWORD`  | SonarQube password (depends on your authentication method)             | _none_ |

| `SONAR_BASE_ARGS`        | SonarQube [analysis arguments](https://docs.sonarqube.org/latest/analysis/analysis-parameters/) | `sonar:sonar -Dsonar.links.homepage=${CI_PROJECT_URL} -Dsonar.links.ci=${CI_PROJECT_URL}/-/pipelines -Dsonar.links.issue=${CI_PROJECT_URL}/-/issues` |

| `SONAR_QUALITY_GATE_ENABLED` | Set to `true` to enable SonarQube [Quality Gate](https://docs.sonarqube.org/latest/user-guide/quality-gates/) verification.<br/>_Uses `sonar.qualitygate.wait` parameter ([see doc](https://docs.sonarqube.org/latest/analysis/ci-integration-overview/#header-1))._ | _none_ (disabled) |

| `SONAR_BASE_ARGS`        | SonarQube [analysis arguments](https://docs.sonarsource.com/sonarqube/latest/analyzing-source-code/analysis-parameters/) | `sonar:sonar -Dsonar.links.homepage=${CI_PROJECT_URL} -Dsonar.links.ci=${CI_PROJECT_URL}/-/pipelines -Dsonar.links.issue=${CI_PROJECT_URL}/-/issues` |

| `SONAR_QUALITY_GATE_ENABLED` | Set to `true` to enable SonarQube [Quality Gate](https://docs.sonarsource.com/sonarqube/latest/user-guide/quality-gates/) verification.<br/>_Uses `sonar.qualitygate.wait` parameter ([see doc](https://docs.sonarsource.com/sonarqube/latest/analyzing-source-code/ci-integration/overview/#quality-gate-fails))._ | _none_ (disabled) |

#### Recommended minimal configuration

1. set the `SONAR_HOST_URL` value either in your `.gitlab-ci.yml` file or as a project or group variable (:warning: setting it as a group variable will enable the SonarQube analysis for all the children projects),

2. define your SonarQube credentials (:lock: `SONAR_TOKEN` or `SONAR_LOGIN` & :lock: `SONAR_PASSWORD`) as project or group variables,

3. configure the project SonarQube settings in the `pom.xml` file (:warning: the [SonarScanner for Maven](https://docs.sonarsource.com/sonarqube/latest/analyzing-source-code/scanners/sonarscanner-for-maven/#configuring-analysis) completely ignores the `sonar-project.properties` file):

    ```xml

    <properties>

      <!-- the SonarQube project key -->

      <sonar.projectKey>write-key-here</sonar.projectKey>

      <!-- additional SonarQube settings can go here -->

      ...

    </properties>

    ```

    More info about [SonarQube settings](https://docs.sonarsource.com/sonarqube/latest/analyzing-source-code/scanners/sonarscanner-for-maven/#analyzing)

:warning: if using [SonarCloud](https://sonarcloud.io/) (a cloud-based SonarQube-as-a-Service), you'll have to define the additional `sonar.organization` property ([see mandatory-parameters](https://docs.sonarcloud.io/advanced-setup/analysis-parameters/#mandatory-parameters)).

:information_source: As SonarCloud determined the `organization` and `projectKey` properties from the project's GitLab context when importing the project, you can reuse the predefined GitLab variables as follows in your `pom.xml`:

```xml

<properties>

  <!-- SonarCloud settings -->

  <sonar.organization>${env.CI_PROJECT_ROOT_NAMESPACE}</sonar.organization>

  <sonar.projectKey>${env.CI_PROJECT_ROOT_NAMESPACE}_${env.CI_PROJECT_NAME}</sonar.projectKey>

</properties>

```

#### Automatic Branch Analysis & Merge Request Analysis

This template relies on SonarScanner's [GitLab integration](https://docs.sonarqube.org/latest/analysis/gitlab-integration), that is able to auto-detect whether to launch Branch Analysis or Merge Request Analysis

This template relies on SonarScanner's [GitLab integration](https://docs.sonarsource.com/sonarqube/latest/devops-platform-integration/gitlab-integration/), which is able to auto-detect whether to launch Branch Analysis or Merge Request Analysis

from GitLab's environment variables.

:warning: This feature also depends on your SonarQube server version and license.

> :information_source: See [Usage](https://to-be-continuous.gitlab.io/doc/usage/#example-3-disable-go-mod-outdated-job) 

> for more information about disabling any job that MAY not be required in a project or group.

Without disabling the job, you can still exclude a particular project by defining a property `<sonar.skip>true</sonar.skip>` in the pom.xml of the project or module you want to exclude.

### `mvn-dependency-check` job

This job enables a manual [Dependency-Check](https://jeremylong.github.io/DependencyCheck/dependency-check-maven/configuration.html)

variables:

```