updated license, style, copyright

[maurafortino]

What's Included:

• (unify) Use SPDX for copyright and reuse. #577
• (unify) Update code style. #578
• (unify) Fix linting errors and enable checking. #579

[codecov]

Codecov Report

Merging #608 (ed444a7) into main (3ed6301) will not change coverage.
Report is 53 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #608   +/-   ##
=======================================
  Coverage   63.46%   63.46%           
=======================================
  Files          18       18           
  Lines        1300     1300           
=======================================
  Hits          825      825           
  Misses        455      455           
  Partials       20       20           

Flag	Coverage Δ
unittests	63.46% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
chrysom/basicClient.go	85.71% <ø> (ø)
chrysom/listenerClient.go	87.95% <ø> (ø)
chrysom/metrics.go	0.00% <ø> (ø)
chrysom/pushResult.go	0.00% <ø> (ø)
chrysom/store.go	0.00% <ø> (ø)
store/cassandra/db.go	0.00% <ø> (ø)
store/cassandra/executer.go	0.00% <ø> (ø)
store/dynamodb/db.go	44.44% <ø> (ø)
store/dynamodb/instrumenting.go	100.00% <ø> (ø)
store/dynamodb/service.go	83.81% <ø> (ø)
... and 8 more