Add Railhook to Messaging

[vadymkykalo]

Suggestion type

• Project
• Resource

Checklist

• I searched the list and existing issues for duplicates.
• I changed README_SOURCE.md, not the generated README.md.
• This pull request contains one suggestion.
• The suggestion is relevant to Java or the JVM and fits its chosen category.
• I used the canonical project or resource link.
• The suggestion is current and maintained.
• The concise, neutral description explains its distinguishing value and ends with punctuation.
• Licensing is clear and any restrictive terms are disclosed where applicable.

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Disclosure: I am the author of Railhook. Self-promotion, submitted under the
"reviewed carefully but welcome" clause in CONTRIBUTING.md — please judge it on
the same criteria as anything else, and close it if it does not clear the bar.
This pull request was prepared with Claude Code on my behalf.

Railhook is a Java 17 / Spring Boot webhook gateway (PostgreSQL transactional
outbox, Kafka, Redis), MIT licensed. What distinguishes it from the existing
Svix entry: it is a server you run rather than a client library, and it covers
both directions — outbound delivery to your customers' endpoints (Standard
Webhooks signatures, a fixed retry ladder, per-endpoint ordering, bulk replay
of failures) and inbound receipt from providers (Stripe, GitHub, GitLab,
Shopify, Slack, Twilio signature verification, deduplication, forwarding to
internal services).

First release v1.0.0 in December 2025, 59 tagged releases since, currently
2.24.0 in production. It is a young project with few stars; I would rather say
so here than have it discovered in review.

🤖 Generated with Claude Code

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Summary by cubic

Adds Railhook to the Messaging tools list in README_SOURCE.md.

Railhook is a self-hosted webhook gateway (Java 17 / Spring Boot) that covers both directions: outbound delivery to subscriber endpoints with signed webhooks, retries, per-endpoint ordering, and replay, plus inbound receipt from providers like Stripe, GitHub, GitLab, Shopify, Slack, and Twilio with signature verification, deduplication, and forwarding. It complements the existing Svix entry, which is a client library rather than a server you run.

^{Written for commit a0cb945. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}