Add unique constraint to alias

[falkecarlsen]

No description provided.

[codecov-commenter]

Codecov Report

Merging #307 (bd20d61) into next (f1fb107) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             next     #307   +/-   ##
=======================================
  Coverage   82.84%   82.84%           
=======================================
  Files          31       31           
  Lines        2623     2623           
  Branches      188      188           
=======================================
  Hits         2173     2173           
  Misses        418      418           
  Partials       32       32           

Impacted Files	Coverage Δ
stregsystem/models.py	88.18% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f1fb107...bd20d61. Read the comment docs.