Use SPDX license expression for project metadata

[cdce8p]

What do these changes do?

SSIA

Are there changes in behavior for the user?

Related issue number

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.47%. Comparing base (0f0305c) to head (217ad5e).
⚠️ Report is 61 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##            master     #445      +/-   ##
===========================================
- Coverage   100.00%   98.47%   -1.53%     
===========================================
  Files            1        1              
  Lines          116      131      +15     
  Branches        19       16       -3     
===========================================
+ Hits           116      129      +13     
- Misses           0        2       +2     

Flag	Coverage Δ
unit	97.70% <ø> (-0.57%)	⬇️

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