docs(event-handler): update to new APIs before release

[dreamorosi]

Summary

Changes

Please provide a summary of what's being changed

This PR brings general updates to the doc page for Event Handler HTTP, namely:

• Update relevant code snippets to match new middleware signature
• Update relevant code snippets to match new route handler signature
• Update relevant code snippets to match new error handler return type
• Update "Route Prefixes" section to reflect that the feature is now available
• Add a callout about always awaiting the next() call in custom middleware functions
• Add a callout about throwing errors anywhere
• Line highlighting mismatches in code snippets

Please add the issue number below, if no issue is present the PR might get blocked and not be reviewed

Issue number: closes #4541

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[sdangol]

On the Middleware section, we have the params as the argument there as well. Same on the mermaid diagrams

[sdangol]

Missed a .request in here as well

[dreamorosi]

Good spots, I fixed both issues and also update the mermaid diagrams to use await next() instead of next().

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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