fix: Threshold domain models mapping, response types for DashboardService

[bednar]

Closes #288
Closes #282

Proposed Changes

1. Use correct mapping for Threshold to be able use Check API.
2. Use correct response types for DashboardService.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• pytest tests completes successfully
• Commit messages are in semantic format
• Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Merging #290 (2325973) into master (025e97e) will increase coverage by 0.23%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #290      +/-   ##
==========================================
+ Coverage   92.38%   92.61%   +0.23%     
==========================================
  Files          27       27              
  Lines        2168     2168              
==========================================
+ Hits         2003     2008       +5     
+ Misses        165      160       -5     

Impacted Files	Coverage Δ
influxdb_client/api_client.py	68.91% <0.00%> (+1.12%)	⬆️
influxdb_client/client/util/date_utils.py	96.29% <0.00%> (+7.40%)	⬆️

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