Detect repeating fields using field labels, enabling admin key to be set

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 60.76%. Comparing base (23e6eca) to head (3bbd02c). Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
meshtastic/__main__.py	20.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #672 +/- ## ======================================= Coverage 60.76% 60.76% ======================================= Files 24 24 Lines 3663 3663 ======================================= Hits 2226 2226 Misses 1437 1437 ``` | [Flag](https://app.codecov.io/gh/meshtastic/python/pull/672/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=meshtastic) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/meshtastic/python/pull/672/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=meshtastic) | `60.76% <20.00%> (ø)` | | 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=meshtastic#carryforward-flags-in-the-pull-request-comment) to find out more.

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