378 Fix problem with IDateTimeContent BSON serialization/deserialization

[dzmitryk-kontent-ai]

Motivation

#378

Checklist

• Code follows coding conventions held in this repo
• Automated tests have been added
• Tests are passing
• Docs have been updated (if applicable)
• Temporary settings (e.g. variables used during development and testing) have been reverted to defaults

How to test

If manual testing is required, what are the steps?

[codecov]

Codecov Report

Merging #379 (afcabb2) into master (46abeb7) will increase coverage by 0.06%.
Report is 4 commits behind head on master.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #379      +/-   ##
==========================================
+ Coverage   88.48%   88.55%   +0.06%     
==========================================
  Files         128      128              
  Lines        2753     2761       +8     
  Branches      345      345              
==========================================
+ Hits         2436     2445       +9     
  Misses        185      185              
+ Partials      132      131       -1     

Files Changed	Coverage Δ
...Delivery/ContentItems/DateTimes/DateTimeContent.cs	100.00% <ø> (ø)
....Delivery.Abstractions/DeliveryClientExtensions.cs	100.00% <100.00%> (ø)
...very.Caching/Extensions/SerializationExtensions.cs	89.28% <100.00%> (+2.32%)	⬆️

... and 1 file with indirect coverage changes

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[Simply007]

LGTM!