[erlang] erlang-server generator fixes

[kpy3]

Current erlang-server generates code with errors which will always crash on key authorisation. This PR fix them and also has minor performance improvements for map updates.

@tsloughter

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[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[kpy3]

@wing328 thanks for pointing, fixed name and email, added back pgp signature. :)

[wing328]

cc @NelsonVides who has made a lot of contributions to the erlang-server generator recently.

[NelsonVides]

Lovely! Thank you for the contribution!

[NelsonVides]

Right, so this needed to be a binary, that looks good 👌🏽

[NelsonVides]

For a moment I feared this would be a breaking change, but actually, this is really a bugfix, the callback was declared as api_key_callback/2 and dialyzer would complain, so the previous code would fail to bind to the right function and crash. Awesome find, thank you very much!