see #2623

To test the prototype / mock, visit the Details View of a Child record use the "Link external profile" button in the form.

TODOs

• load ESCO skill details (name, description) via API
• loading indicator for ESCO Skill requests
• Skills field doesn't update immediately yet after clicking "Update data"
• "Unlink" is not saved (resets to previous external ID after reload)
• linking an user-profile is possible in "non-edit" mode (?)
• search parameters (e.g. name) are only used if the entity was saved (should take the current form value immediately)
• make details for matching configurable (Entity Type, fields for search (fullName, email, ...), etc.)
• implement a bulk import/link workflow

Refactorings:

• implement a re-usable ErrorDetailsComponent (for LinkExternalProfileDialogComponent as well as ReportingComponent and other places where we need to both display a simple message and give access to technical error details for experts)
• make the Bulk Actions configurable through a service instead of hard-coding actions into EntityListComponent (--> similar or combined (?) system to the EntityActionsMenuService)