Batch linking REST API endpoint

How: Add endpoint for batch-linking one entity to many other entities.

Why: It is often the case that we have a set of entities that we need to link to another, such as when linking a set of resources to a product. Adding these links one-by-one requires a lot of API calls, with an increased overhead and chance of errors when compared with a lower amount of batch calls.

For Who: Developers

Impact: Improved performance when creating links

Additional context: This API endpoint (/api/v1.0.0/links/batch/add) has already been released to the public "by accident". Having had the opportunity to make use of it before entering a broken state, we were generally experiencing good results. This idea is made in the hope that it will swiftly return as an official public endpoint.

A couple of suggestions based on my experience with the endpoint:

• Check if the LinkTypeId being sent is valid for the entities being linked

• Add the links in the order the target entity ids is sent, instead of doing it from lowest id to highest