* Add "subtasks" type action board
* Each column will contain a work package
* The cards in the column are filtered to show only the selected work package's children
* All work packages in the project that are elligable to be a parent may be selected as a column (no milestones)
* Work packages can be dragged and dropped between parents

**Open for discussion**

* Permission handling if selected work package is located in a subproject

**Related pull request**: https://github.com/opf/openproject/pull/8504

**Notes**

* Create a new action service
* To change the parent relation: frontend/src/app/components/wp-relations/wp-relations-hierarchy/wp-relations-hierarchy.service.ts
* Column creation modal should contain a typeahead

**TODO**

* Begin of the insertion[x]End of the insertion Upgrade account to have access to boards Begin of the insertion



**MORE INFO**
You will need two things:

1. The actual filter value for the columns, this is `parent = <selected ID for the colum>` meaning: Give me all children of &lt;selected ID&gt;
2. The applicable work packages. This will be all work packages in the current project that CAN be a parent. Which is every work package except for milestones

The second one is a bit more complicated. You will have to

* Load all Types to find out the IDs of all types which are not milestones
* Load all work packages in the current project which have a type ID contained in one of the above

The first one: Inject `TypeDmService` and get the types `typeDmService.loadAll().then(types => types.filter(type => !type.isMilestone))` (this should be moved into a \`TypeCacheService\` but there isn&#39;t one at the momentThe second one then is rather easy

      this.halResourceService
        .get(
          this.pathHelper.api.v3.withOptionalProject(currentProjectId).work\_packages.toPath()
          { filters: buildApiV3Filter(&#39;type&#39;, &#39;=&#39;, types.map(type =&gt; type.id)).toJson() }
        )

it calls a `GET /api/v3/projects/<current project id>/work_packages?filter=[{ type: { operator: '=', values: [1,2,3...] }]`

and this will get all work packages of the project that are eligable to be a parent - they might also already be a parent but that shouldn&#39;t matter (editado) 

now the problem is that this call might result in a large number of work packages, which is why in the Add List ... Modal we need to use this query with an autocompleter

but that could be a separate refactoring I can do laterEnd of the insertion