This is a temporary refactoring stub, that is planned to be removed
after removing legacy config processor.

As for now, we keep this class inside a oryginal config processor class.
We will move implementation to this class and delegate to it from
current config processor.

After original gitlab ci yaml processor not longer has relevant
impelemntation we will replace it with new configuration class.

Favor `unless` over `if` for negative conditions
(or control flow ||).

See #17478

Closes #17406

add 'triggers' keyword to gitlab-ci.yml 'only' and 'except' fields to allow control over whether triggers will cause jobs to run

This allows to reuse one job as a template for another one:

```
job1: &JOBTMPL
  script: execute-script-for-job

job2: *JOBTMPL

```

This also helps to solve some of the issues in #342
Signed-off-by: NPascal Bach <pascal.bach@siemens.com>
Signed-off-by: NFabio Huser <fabio.huser@siemens.com>