Add LOG_LEVEL config option and improve LDAP sync resiliency

[codecov[bot]]

Codecov Report

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

Comparison is base (896e0fd) 94.73% compared to head (e2984d8) 94.77%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #610 +/- ## ========================================== + Coverage 94.73% 94.77% +0.04% ========================================== Files 75 75 Lines 4311 4310 -1 ========================================== + Hits 4084 4085 +1 + Misses 227 225 -2 ``` | [Flag](https://app.codecov.io/gh/amiv-eth/amivapi/pull/610/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=amiv-eth) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/amiv-eth/amivapi/pull/610/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=amiv-eth) | `94.77% <100.00%> (+0.04%)` | :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=amiv-eth#carryforward-flags-in-the-pull-request-comment) to find out more.

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