ref https://github.com/TryGhost/Team/issues/2421
- added the Mentions API endpoint to Admin
- setup initial mention model in the Ember Store to be able to dev with the endpoint
- added basic routing to access the `/mentions` page that is currently behind feature flags
- Setup basic testing with a mirage mock endpoint.
no issue
`ember-cli-mirage` replaced the use of a default function export with a `createServer` function that applies config and deprecated the older mirage config export style. It will also soon drop support of the separate `testConfig` export we used for defining our test routes.
- switched to the newer `return createServer(config);` server configuration approach
- extracted dev and test routes into separate files for a cleaner base config
