Add support for metric to track the maximum number of devices permitted to connect to a Talaria instance.

[ChaitanyaSingla]

We need to introduce a metric in Talaria that reflects the maximum number of devices permitted to connect to a Talaria instance. This pull request includes the addition of a metric to monitor the maximum allowed device connections for Talaria.

Reference issue for this MR: #299

cc: @Sachin4403

[CLAassistant]

All committers have signed the CLA.

[ChaitanyaSingla]

@johnabass I have already signed the CLA agreement, but it is still showing as pending.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 58.60%. Comparing base (94a661b) to head (6745563).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
main.go	0.00%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #454      +/-   ##
==========================================
- Coverage   58.91%   58.60%   -0.32%     
==========================================
  Files          18       18              
  Lines        1862     1872      +10     
==========================================
  Hits         1097     1097              
- Misses        723      733      +10     
  Partials       42       42              

Flag	Coverage Δ
unittests	58.60% <0.00%> (-0.32%)	⬇️

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[denopink]

lgtm! 🍻