Fix default charset in Undertow consumer when Content-Type omits charset

[Croway]

Summary

• Undertow's getRequestCharset() defaults to ISO-8859-1 when no charset is specified in the Content-Type header, causing UTF-8 encoded request bodies (e.g. application/json) to be decoded incorrectly
• Only set the exchange charset property when explicitly specified in the header, letting Camel's type conversion default to UTF-8 — matching the behavior of DefaultHttpBinding
• Added test that sends JSON with non-ASCII UTF-8 characters and Content-Type: application/json (no charset)

Test plan

• New test RestUndertowHttpPostJsonPojoCharsetTest fails before fix, passes after
• All 161 existing Undertow tests pass

[github-actions]

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[gnodet]

Nice fix, thanks @Croway! 👍

The change correctly aligns UndertowConsumer with DefaultHttpBinding's behavior — only setting the charset property when explicitly specified in the Content-Type header, rather than relying on Undertow's getRequestCharset() which defaults to ISO-8859-1.

The test coverage is good — sending non-ASCII UTF-8 characters with Content-Type: application/json (no charset) is exactly the right scenario to validate.

One minor note: there's no JIRA ticket linked. For changelog traceability a JIRA issue is typically preferred even for bug fixes, but not blocking.

LGTM ✅

Claude Code on behalf of Guillaume Nodet

[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud