feat: Add verifiable credential store

[sandrask]

Store verifiable credential into verifiable credential store during anchor writing.

Closes #826

Signed-off-by: Sandra Vrtikapa sandra.vrtikapa@securekey.com

[codecov]

Codecov Report

Merging #828 (f95fccc) into main (4aedfef) will decrease coverage by 0.04%.
The diff coverage is 86.20%.

@@            Coverage Diff             @@
##             main     #828      +/-   ##
==========================================
- Coverage   89.44%   89.39%   -0.05%     
==========================================
  Files         144      144              
  Lines       12700    12725      +25     
==========================================
+ Hits        11359    11375      +16     
- Misses        825      832       +7     
- Partials      516      518       +2     

Impacted Files	Coverage Δ
pkg/store/anchorevent/store.go	100.00% <ø> (ø)
cmd/orb-server/startcmd/start.go	73.70% <75.00%> (-0.11%)	⬇️
pkg/anchor/writer/writer.go	91.51% <90.47%> (-0.09%)	⬇️
...pub/service/inbox/httpsubscriber/httpsubscriber.go	90.12% <0.00%> (-9.88%)	⬇️
pkg/observer/pubsub.go	97.22% <0.00%> (+2.77%)	⬆️

---

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 4aedfef...f95fccc. Read the comment docs.