spec!: add support for several topic matcher types, including URL Pattern

[dunglas]

Replaces #831 with a more flexible and future-proof approach.

Summary

• In addition to URI templates, regular expressions, URL patterns and CEL expressions are now supported
• the topic query parameter becomes match and now only supports exact matching
• new query parameters match{MatchType} are introduced
  • by default, matchRegexp, matchURLPattern, matchCEL, and matchURITemplate are defined
  • hub can implement custom matcher types
  • future updates may introduce new matcher types
• it's now possible to include per-topic (or topic matcher) payloads (replaces feat: payload for a specific topic #945)
• the JWT format has been updated to match these new capabilities
• the subscription API format has been updated to match these new capabilities

The official hub will be able to support both the current and new protocols simultaneously (no hard BC break).

TODO:

• update all examples

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[soyuka]

This is still ongoing work

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Copilot]

Pull request overview

This PR updates the Mercure protocol specification to support multiple topic matcher types (Exact, Regexp, URLPattern, CEL, optional URI Template), introduces match* subscription query parameters, and extends the JWT/subscription formats to support per-matcher payloads.

Changes:

• Reworks subscription semantics around match + match{Type} query parameters with case-insensitive parameter names and 501 handling for unsupported matcher types.
• Defines matcher types (Exact/Regexp/URLPattern/CEL/URITemplate) and updates authorization (JWT) semantics to use typed matcher objects.
• Updates Active Subscriptions (events + API) and examples to include matcher type + matcher value, plus per-matcher payloads.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 6 comments.

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