Improve add items

[soininen]

This PR fixes a bug that allowed adding items that didn't have all unique keys.

Also, it is now possible to add an entity class or entity item without a name if dimension_name_list or element_name_list is given. In this case the name will be generated from the list.

No associated issue

Checklist before merging

• [x] Documentation (also in Toolbox repo) is up-to-date
• [x] Release notes in Toolbox repo have been updated
• [x] Unit tests have been added/updated accordingly
• [x] Code has been formatted by black
• [x] Unit tests pass

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 78.26%. Comparing base (bf66936) to head (f3eab6d).

:exclamation: Current head f3eab6d differs from pull request most recent head 91553cc

Please upload reports for the commit 91553cc to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #409 +/- ## ========================================== + Coverage 78.19% 78.26% +0.07% ========================================== Files 76 76 Lines 9510 9534 +24 Branches 2016 2023 +7 ========================================== + Hits 7436 7462 +26 + Misses 1738 1737 -1 + Partials 336 335 -1 ```

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