Add copyright for all go files

[SimFG]

/kind improvement

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b87d371) 81.64% compared to head (0cb050e) 81.64%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #34   +/-   ##
=======================================
  Coverage   81.64%   81.64%           
=======================================
  Files          38       38           
  Lines        4085     4085           
=======================================
  Hits         3335     3335           
  Misses        625      625           
  Partials      125      125           

Files	Coverage Δ
core/api/data_handler.go	88.88% <ø> (ø)
core/api/message_manager.go	100.00% <ø> (ø)
core/api/meta_op.go	100.00% <ø> (ø)
core/api/reader.go	100.00% <ø> (ø)
core/api/replicate_manager.go	68.42% <ø> (ø)
core/api/writer.go	100.00% <ø> (ø)
core/reader/channel_reader.go	96.73% <ø> (ø)
core/reader/collection_reader.go	79.50% <ø> (ø)
core/reader/data_barrier.go	100.00% <ø> (ø)
core/reader/etcd_op.go	84.07% <ø> (ø)
... and 28 more