Add integration test for ElemRoutes

**Motivation**
* There are no integration tests for ElemRoutes
* The `tag` and `type` query parameters in the ElemRoutes are untested
* Streaming elems using the DeltaClient with `tag` and `type` parameters is untested

Start by locating the ElemRoutes and DeltaClient entry points and any existing integration-test conventions in the repository. Add coverage for the tag and type query parameters, including streaming elems through DeltaClient with those parameters. Done means the integration tests exercise all cases named in the issue and pass.

Written by the indexing model from the issue text.