Adds reference_id setting

[o087D]

Enables end user to set the value for 'reference_id' if operating as a server in stratum 1, as discussed in #1718

[codecov]

Codecov Report

Attention: Patch coverage is 87.75510% with 6 lines in your changes missing coverage. Please review.

Project coverage is 81.43%. Comparing base (badb4f1) to head (2f300a6).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
ntp-proto/src/config.rs	91.48%	4 Missing ⚠️
ntp-proto/src/system.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1815      +/-   ##
==========================================
+ Coverage   81.41%   81.43%   +0.01%     
==========================================
  Files          68       68              
  Lines       21610    21659      +49     
==========================================
+ Hits        17594    17637      +43     
- Misses       4016     4022       +6     

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[davidv1992]

This looks like a good design to me. Thanks for the contribution.

[davidv1992]

@rnijveld can you take a short look at this, in particular if you agree with the new setting name and placement?

[rnijveld]

This looks good to me as well, I think the synchronization section is probably the best section for this!

[rnijveld]

Thanks for the contribution!