fix: Create Event copy with all required fields

[lenny-goodell]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

FilterByResource creates copy of Event without all required fields
Unit tests doesn't validate Event is valid after filtering.

Issue Number: #922

What is the new behavior?

FilterByResource now creates copy of Event with all required fields
Unit tests now validates Event is valid after filtering.

Does this PR introduce a breaking change?

• Yes
• No

Are there any new imports or modules? If so, what are they used for and why?

Are there any specific instructions or things that should be known prior to reviewing?

Other information

[codecov-commenter]

Codecov Report

Merging #925 (5f922c3) into main (83c633e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #925   +/-   ##
=======================================
  Coverage   65.33%   65.33%           
=======================================
  Files          33       33           
  Lines        2345     2345           
=======================================
  Hits         1532     1532           
  Misses        722      722           
  Partials       91       91           

Impacted Files	Coverage Δ
pkg/transforms/filter.go	97.89% <100.00%> (ø)

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