CD and OAS: take configuration from the registered plugin and JsonApi4j instead of servlet-context copies, plus small cleanups #218

The CD filter and the OAS servlet took their configuration from several places at once: servlet-context attributes, a separately built executor, and a raw ObjectMapper lookup. In a plain servlet setup, a plugin's properties existed twice: the instance registered in the PluginRegistry (validated, and shown in the Meta API's config) and a copy the plugin's servlet initializer read from the config file, which the filter or servlet actually used. The two could disagree.

Changes

• CompoundDocsFilter gets what it needs from JsonApi4j, with one initJsonApi4j call:
  • its properties from jsonApi4j.getPluginRegistry().configOf(CompoundDocsProperties.class) instead of a servlet-context attribute;
  • the root path from jsonApi4j.getProperties();
  • the executor from jsonApi4j.getExecutor();
  • the error handlers from jsonApi4j.getErrorHandlers().
• OasServlet reads its properties from configOf(OasProperties.class), and gets its ObjectMapper through initObjectMapper. Before, it used a raw attribute lookup with no fallback, so objectMapper could be null.
• A plugin enabled in config but not registered in the PluginRegistry now logs a warning naming the cause, and its filter or servlet stays inactive. Before, it ran with a separate copy of the configuration.
• CompoundDocsResolver and CachingCompoundDocsFetcher take an Executor instead of an ExecutorService. They only call supplyAsync, and existing callers still compile.
• Small fixes: the log typo "initialization failer", and the stale comment on the Quarkus sample's pinned native test port.

Tests

• INCLUDED_ONLY with an include path that continues through a primary resource: the resource is repeated exactly once, as the fetched copy with the linkage the path needed.
• Spring wiring: cd.deduplication binds, and the nested mapping entries bind (url, maxBatchSize, propagateCredentials, and a same-app entry with only a batch size).

Verified: the packaged Quarkus app binds nested mapping entries from environment variables set at runtime: JSONAPI4J_CD_MAPPING_DEFAULT_URL, and JSONAPI4J_CD_MAPPING_<TYPE>_URL for a type that appears nowhere in the config. This also holds when the config has no mapping keys at all.

Behaviour change: in a plain servlet setup, CD or OAS enabled in config but not registered in the PluginRegistry is no longer served. Spring and Quarkus always register the plugin.