[Enh]: `dab validate` Output to File for CICD

[JerryNixon]

The flag dab validate -output:results.xml extends dab validate to support outputting the validation results in a machine-readable XML format useful for CI/CD pipelines. This allows for automated validation of configuration files, where any validation errors will be written to the specified XML file for further processing or reporting just like unit test. It's okay to still output to the console.

Sample file

The JUnit XML format is widely used for reporting test results and is supported by most CI/CD tools (Jenkins, GitLab CI, Azure DevOps, etc.). You can find the JUnit XML schema reference and examples at the following link: JUnit XML Format.

<testsuites>
  <testsuite name="DABConfigurationValidation" tests="4" failures="3">

    <!-- Test Case for Missing Connection String -->
    <testcase classname="DataSourceValidation" name="Missing Connection String">
      <failure message="Connection-string is not present in the data-source.">
        The data-source section is missing the required 'connection-string' field.
      </failure>
    </testcase>

    <!-- Test Case for Empty Entities Array -->
    <testcase classname="EntityValidation" name="Entities Array is Empty">
      <failure message="The entities[] array has no entities.">
        The entities array in the configuration is empty. Please define at least one entity.
      </failure>
    </testcase>

    <!-- Test Case for Invalid Runtime Host Mode -->
    <testcase classname="RuntimeHostValidation" name="Invalid Host Mode">
      <failure message="runtime/host/mode has an invalid value.">
        The value 'abc' for runtime/host/mode is invalid. Expected values are 'development', 'production', or 'staging'.
      </failure>
    </testcase>

    <!-- Test Case for Valid Authorization Provider -->
    <testcase classname="AuthorizationProviderValidation" name="Valid Authorization Provider">
      <!-- No failure, this passes -->
    </testcase>

  </testsuite>
</testsuites>