feat: add Google Chat thread support

[taisph]

trafficstars

Support posting messages to a chat thread based on an arbitrary key.

Example threads:

See Chat API create message query parameters.

[codecov[bot]]

Codecov Report

Base: 49.21% // Head: 49.38% // Increases project coverage by +0.16% :tada:

Coverage data is based on head (cd14e6e) compared to base (b605032). Patch coverage: 70.00% of modified lines in pull request are covered.

:exclamation: Current head cd14e6e differs from pull request most recent head af116bd. Consider uploading reports for the commit af116bd to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #95      +/-   ##
==========================================
+ Coverage   49.21%   49.38%   +0.16%     
==========================================
  Files          31       31              
  Lines        1855     1873      +18     
==========================================
+ Hits          913      925      +12     
- Misses        743      746       +3     
- Partials      199      202       +3     

Impacted Files	Coverage Δ
pkg/services/googlechat.go	62.16% <70.00%> (+1.44%)	:arrow_up:

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[pasha-codefresh]

LGTM, thank you!