bugfix: assign usertasks to the current user

[lmoesle]

Changes

• Users can assign usertasks only to themself
• Allow more configuration options by defining beans in Taskconfiguration

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 46.12%. Comparing base (1a8fce0) to head (bd8bc8c).

Files	Patch %	Lines
...ranum/platform/tasklist/TasklistConfiguration.java	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #412 +/- ## ========================================= Coverage 46.11% 46.12% - Complexity 397 398 +1 ========================================= Files 187 187 Lines 2084 2088 +4 Branches 110 110 ========================================= + Hits 961 963 +2 - Misses 1089 1091 +2 Partials 34 34 ``` | [Flag](https://app.codecov.io/gh/Miragon/miranum/pull/412/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Miragon) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/Miragon/miranum/pull/412/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Miragon) | `46.12% <50.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Miragon#carryforward-flags-in-the-pull-request-comment) to find out more.

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