fix: add error checking when creating verification code

[hperl]

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Merging #3328 (b4c2cf3) into master (3485204) will decrease coverage by 0.11%.
The diff coverage is 71.42%.

❗ Current head b4c2cf3 differs from pull request most recent head 266a5a9. Consider uploading reports for the commit 266a5a9 to get more accurate results

@@            Coverage Diff             @@
##           master    #3328      +/-   ##
==========================================
- Coverage   78.20%   78.09%   -0.11%     
==========================================
  Files         325      325              
  Lines       21079    21080       +1     
==========================================
- Hits        16484    16463      -21     
- Misses       3370     3386      +16     
- Partials     1225     1231       +6     

Impacted Files	Coverage Δ
persistence/sql/persister_verification.go	83.12% <66.66%> (-1.16%)	⬇️
selfservice/strategy/code/verification_code.go	50.00% <100.00%> (ø)

... and 3 files with indirect coverage changes