updated licensing, code style

[maurafortino]

What's included:

• (unify) Use SPDX for copyright and reuse. #443
• (unify) Update code style. #444
• (unify) Fix license errors and enable checking. #445

[codecov]

Codecov Report

Merging #451 (92f373b) into main (feb2ca0) will not change coverage.
Report is 5 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #451   +/-   ##
=======================================
  Coverage   45.63%   45.63%           
=======================================
  Files          15       15           
  Lines        1168     1168           
=======================================
  Hits          533      533           
  Misses        623      623           
  Partials       12       12           

Flag	Coverage Δ
unittests	45.63% <ø> (ø)

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

Files Changed	Coverage Δ
auth.go	0.00% <ø> (ø)
basculeLogging.go	100.00% <ø> (ø)
main.go	0.00% <ø> (ø)
primaryHandler.go	0.00% <ø> (ø)
routes.go	0.00% <ø> (ø)
setup.go	0.00% <ø> (ø)
stat/endpoint.go	100.00% <ø> (ø)
stat/service.go	84.21% <ø> (ø)
stat/transport.go	75.00% <ø> (ø)
transaction/errors.go	86.36% <ø> (ø)
... and 5 more