The Wikimedia OpenAPI linter requires a root-level `externalDocs` object in every OAD (`wikimedia-require-external-docs` rule, severity: error). The framework never generates this field and provides no way to set it.
##Context
`ModuleSpecHandler::run()` builds the top-level document with only five keys: `openapi`, `info`, `servers`, `paths`, `components`. There is no `externalDocs` and no way to supply one from a module definition file:
$spec = [
'openapi' => '3.0.0',
'info' => ...,
'servers' => ...,
'paths' => ...,
'components' => ...,
// ← no 'externalDocs'
];
Note: `externalDocs` at the *operation* level is already supported (it is in `$oasKeys` in `SpecBasedModule::makeRouteInfo()`). Only the root-level field is missing.
**4 errors — one per REST module.**
##Conditions of acceptance
- [ ] Support an `externalDocs` key in the module definition `.json` file, readable by `SpecBasedModule` or `ModuleSpecHandler`.
- [ ] When present, include it at the root of the document generated by `ModuleSpecHandler::run()`.
- [ ] Add a unit test verifying the field is passed through correctly.
##Related tasks
- T425942 (spike that identified this gap)