CAMEL-23597: camel-solr - align Exchange header prefix constants with Camel naming convention

[oscerd]

Summary

Renames the two Exchange header prefix constants in SolrConstants (camel-solr) to follow the CamelXxx naming convention already used by the other constants in the same file, completing the alignment started in CAMEL-21697 (4.10):

• SolrConstants.HEADER_FIELD_PREFIX value: "SolrField." -> "CamelSolrField."
• SolrConstants.HEADER_PARAM_PREFIX value: "SolrParam." -> "CamelSolrParam."

The Java field names (HEADER_FIELD_PREFIX, HEADER_PARAM_PREFIX) are unchanged, so routes that reference the constants symbolically continue to work without changes. Routes that set the headers by their literal string value (setHeader("SolrField.id", ...) / setHeader("SolrParam.commit", ...)) must be updated to the new prefix — documented in the 4.21 upgrade guide entry added by this PR.

Consistent with the alignment applied in CAMEL-23506 (camel-aws2-sqs / camel-aws2-sns), CAMEL-23508, CAMEL-23510, CAMEL-23515, CAMEL-23516, CAMEL-23522 (camel-mail), CAMEL-23526 (camel-cxf), and CAMEL-23532 (camel-vertx-websocket / camel-atmosphere-websocket / camel-iggy).

What changed

• SolrConstants.java: prefix values renamed.
• SolrProducer.java / SolrRequestConverter.java: inline javadoc comments updated to reference the new literal prefixes.
• SolrInsertAndDeleteTest, SolrPingAndSearchTest, SolrTestSupport: integration-test header literals updated to the new prefixes.
• solr-component.adoc: documentation snippets updated.
• camel-4x-upgrade-guide-4_21.adoc: new === camel-solr upgrade-guide entry mirroring the cxf/mail/aws-sqs notes.

Test plan

• mvn -DskipTests formatter:format impsort:sort install in components/camel-solr — BUILD SUCCESS, no formatter/import diffs.
• Repo-wide search for stale "SolrField." / "SolrParam." literals — only the upgrade-guide entry retains them (deliberate, documenting the old -> new rename).
• No catalog / metadata / endpoint-DSL artifacts reference the prefix values (they are not annotated with @Metadata), so no project-wide regeneration is required.
• Full-reactor mvn clean install -DskipTests runs locally — note: dies at core/camel-xml-io schemagen due to a pre-existing JDK 21 + worktree-path env issue (jaxb2-plugin URL-decodes + in the worktree path as space) that is unrelated to this change; CI will cover the cross-module check.
• CI green.

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Claude Code on behalf of Andrea Cosentino

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

• components/camel-solr
• docs

All tested modules (8 modules)

• Camel :: JBang :: MCP
• Camel :: JBang :: Plugin :: Route Parser
• Camel :: JBang :: Plugin :: TUI
• Camel :: JBang :: Plugin :: Validate
• Camel :: Launcher :: Container
• Camel :: Solr
• Camel :: YAML DSL :: Validator
• Camel :: YAML DSL :: Validator Maven Plugin

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⚙️ View full build and test results

[gnodet]

Looks good — prefix constants correctly renamed from SolrField. / SolrParam. to CamelSolrField. / CamelSolrParam.. Tests comprehensively updated. Upgrade guide entry is well-written with a helpful warning about HeaderFilterStrategy stripping Camel* headers at transport boundaries.

Claude Code on behalf of Guillaume Nodet