[Web] Batch action: Add to groups

[exalate-issue-sync]

Description

User Stories

• As an admin who wants to add multiple users to a group I want to add them all at once so that I dont need to do it step-by-step.

Value

Acceptance Criteria

• Add batchaction "Add to groups" (icon: "add-line")
• action opens modal (see screenshots)
  • Title: "Add to groups"
  • Desc: "Add [n] selected users to groups."
  • Drop: Groups [Same as edit-groups drop but starts always empty]
  • Actions: [Cancel] [Add]
• side quest: if screen size is too small, move batch action button labels into tooltip (like in files app)

Definition of ready

[ ] everybody needs to understand the value written in the user story
[ ] acceptance criteria has to be defined
[ ] all dependencies of the user story need to be identified
[ ] feature should be seen from an end user perspective
[ ] user story has to be estimated
[ ] story points need to be less then 20

Definition of done

• Functional requirements
  [ ] functionality described in the user story works
  [ ] acceptance criteria are fulfilled
• Quality
  [ ] code review happened
  [ ] CI is green
  [ ] critical code received unit tests by the developer
  [ ] e2e test for adding 3 users to 2 groups. for assertion, use group filter and check if users were added.
  [ ] automated tests passed (if automated tests are not available, this test needs to be created and passed
• Non-functional requirements
  [ ] no sonar cloud issues