feat(pool options): add ability to use custom error encoder

[rustatian]

Reason for This PR

• Custom error handler for the static pool.

Description of Changes

• Add pool option to override the default error encoder
• Add tests

License Acceptance

By submitting this pull request, I confirm that my contribution is made under
the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.]
[Reviewer TODO: Verify that these criteria are met. Request changes if not]

• All commits in this PR are signed (git commit -s).
• The reason for this PR is clearly provided (issue no. or explanation).
• The description of changes is clear and encompassing.
• Any required documentation changes (code and docs) are included in this PR.
• Any user-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.

[codecov]

Codecov Report

Merging #6 (e636f37) into master (b23c7a6) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master       #6      +/-   ##
==========================================
+ Coverage   79.71%   79.75%   +0.03%     
==========================================
  Files          19       20       +1     
  Lines        1711     1714       +3     
==========================================
+ Hits         1364     1367       +3     
  Misses        293      293              
  Partials       54       54              

Impacted Files	Coverage Δ
pool/options.go	100.00% <100.00%> (ø)
pool/static_pool.go	71.03% <100.00%> (-0.57%)	⬇️

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