Exposable router to enable client access to datahike embedded in a server

[alekcz]

SUMMARY

Creates a new datahike.http.router namespace that enables embedding Datahike's HTTP server as a library component with a connection registry for hybrid access patterns.

Key Changes:

• New datahike.http.router namespace with route generation and Ring handler creation
• Connection registry enabling local processes to directly access router-managed connections
• Support for Transit+JSON and JSON serialization formats
• Authentication and dev-mode configuration
• Writer route generation for transactional operations
• Three registry API functions: router/get-connection, router/list-connections, router/clear-connections!

Router Features:

• Programmatic route creation without server startup
• Embedded server capability via Ring handlers
• Flexible serialization (Transit, JSON, EDN, raw)
• Token-based authentication with dev-mode bypass
• Route prefixing for reverse proxy scenarios

Connection Registry:

• Store identity-based connection keys (robust, canonical)
• Dual API: config map or store identity vector lookup
• Automatic registration on HTTP connect, cleanup on release
• Perfect consistency across HTTP and direct access methods

Checks

Feature

• Implements an existing feature request. Make sure the feature request has been accepted for implementation before opening a PR.
• Related issues linked using fixes #number
• Integration tests added
• Documentation added
• Architecture Decision Record added
• Formatting checked

ADDITIONAL INFORMATION

Test Coverage:

• Router: 42 tests, 858 assertions, 0 failures
• Comprehensive sync test verifies 4 connection types maintain perfect consistency
• All connection types tested: HTTP CLIENT, MAIN (registry), WRITER, REMOTE-PEER

Example Usage:

;; Create embedded router
(require '[datahike.http.router :as router])
(def handler (router/create-ring-handler :config {:dev-mode true}))
(def server (jetty/run-jetty handler {:port 3000 :join? false}))

;; HTTP client connects (automatically registers connection)
(def conn (client/connect {:store {:backend :file :path "/data/db"}
                           :remote-peer {:backend :datahike-server 
                                        :url "http://localhost:3000"}}))

;; Local process retrieves same connection from registry
(def local-conn (router/get-connection {:store {:backend :file :path "/data/db"}}))

;; Local transactions bypass HTTP, visible to all clients
(d/transact local-conn [{:user/name "Alice"}])

[alekcz]

@whilo could you have a look? I think it's ready.