Workflow in pom is ignored if parent pom already has workflow in it

[neubs-bsi]

Summary of the Bug

Workflow isn't taken from a child pom at all.
If a parent pom has a workflow defined in its tina plugin a workflow in a child pom is not used at all.

Steps to reproduce

• have a parent pom that has a <workflow></workflow> in it's plugin configuration
• have a submodul that has an additional configuration of the plugin in its pom, including an extra workflow step in its configuration via <workflow></workflow>
• execute submodules pom -> extra workflow step is not executed

Acceptance Criteria

• all workflow steps (project + project's parent) get executed
• check for overwrites -> if step in project contradicts that of parent, it should overwrite that configuration

Definition of Done

• Acceptance criteria fulfilled
• A test case is created to reproduce the bug
• A PR is created, the CI infrastructure reports green, the bug test case proves that bug is fixed
• The PR is reviewed and approved
• No TODOs left in the code unless explained in the ticket, if something else is still open, this is summarized in a comment in the issue
• Documentation is updated