[FEATURE] Added tags to accounts and contacts

__Tasks:__
- [ ] adjust entities
- [ ] adjust api
- [ ] adjust UI
- [ ] test coverage
- [ ] gather feedback for my changes

__Informations:__

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| Tests pass?   | yes
| Fixed tickets | [none]
| Doc           | none