Update to SPDX.

[schmidtw]

No description provided.

[codecov]

Codecov Report

Merging #140 (d50cac5) into main (478cc45) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #140   +/-   ##
=======================================
  Coverage   47.79%   47.79%           
=======================================
  Files          24       24           
  Lines        4352     4352           
=======================================
  Hits         2080     2080           
  Misses       2087     2087           
  Partials      185      185           

Flag	Coverage Δ
unittests	47.79% <ø> (ø)

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

Files Changed	Coverage Δ
format.go	69.35% <ø> (ø)
id.go	100.00% <ø> (ø)
messages.go	96.99% <ø> (ø)
messages_codec.go	30.25% <ø> (ø)
messagetype.go	95.12% <ø> (ø)
qos.go	100.00% <ø> (ø)
simpleMessageTypes_validator.go	100.00% <ø> (ø)
spec_validator.go	100.00% <ø> (ø)
utf8.go	90.00% <ø> (ø)
validator.go	100.00% <ø> (ø)
... and 11 more