Support x-ndjson response type for batch element requests

[abelhegedus]

Since 4.0, the POST "get all elements" call ( https://github.com/Open-MBEE/mmsri/blob/a96ad352b98fe9317581f6f179d6058b8c4af2aa/openapi/api-docs.yaml#L917 ) supports streaming x-ndjson response (
https://github.com/Open-MBEE/mmsri/blob/a96ad352b98fe9317581f6f179d6058b8c4af2aa/openapi/api-docs.yaml#L945 )

It would be useful to add this response type to the batch (PUT) requests where requesting the data for a set of elements ( https://github.com/Open-MBEE/mmsri/blob/a96ad352b98fe9317581f6f179d6058b8c4af2aa/openapi/api-docs.yaml#L948 )

[dlamoris]

it makes sense to add support, but one difference between get all and client requested elements is we also return "not found" or "deleted" requested elements in the return json as 'rejected' currently, supporting ndjson means either not returning those or saving and 'marking' them in a compatible way, we're not sure yet