* 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**

* Begin of the insertion~~PermissionEnd of the insertion Begin of the deletion PermissionEnd of the deletion handling if selected work package is located in a Begin of the insertionsubproject~~ onlyEnd of the insertion Begin of the deletion 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**

* [ ] Oliver:
* [ ] Why putFromPromiseIfPristine on subtasks-action.service?
* [ ] What is subtask input for?
* [x] Upgrade account to have access to boards
* [x] Translation not shown (missing "en.js.boards.board\_type.action\_type.subtask")

**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 applicableEnd of the deletion work Begin of the deletion packages. This will be all workEnd of the deletion packages Begin of the insertionfromEnd of the insertion Begin of the deletion in theEnd of the deletion current project Begin of the insertioncanEnd of the insertion Begin of the deletion that CANEnd of the deletion be Begin of the insertionselectedEnd of the insertion Begin of the deletion a parent. Which is every work package except for milestonesEnd of the deletion

Begin of the insertion**Related pull request**: https://github.com/opf/openproject/pull/8504End of the insertion Begin of the deletion ~~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)~~

Finding out all applicable parents is easy now with the `is_milestone` filter.

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 autocompleterEnd of the deletion