[IMPROVE] Missing addCustomField method in MessageBuilder

[matheusbsilva137]

What? ⛵

• Added the addCustomField method in the MessageBuilder class so as to allow developers to add custom fields using the messageBuilder object.

Why? 🤔

This PR is introduced in order to make the MessageBuilder class more complete and consistent, it has been built as a solution to the issue #309.

Links 🌎

Issue #309

PS 👀

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #363 (2f57f3a) into alpha (b358174) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            alpha     #363      +/-   ##
==========================================
+ Coverage   53.22%   53.36%   +0.14%     
==========================================
  Files          86       86              
  Lines        2914     2923       +9     
  Branches      412      415       +3     
==========================================
+ Hits         1551     1560       +9     
  Misses       1363     1363              

Impacted Files	Coverage Δ
src/server/accessors/MessageBuilder.ts	87.38% <100.00%> (+1.11%)	⬆️

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[graywolf336]

Potentially a missing error check. And can you cover the new lines in the tests?

[cuonghuunguyen]

Is there any issue that blocks this PR? It's been here for a very long time

Changes addressed