append_dataset_to_aggregation_list() should optionally put the dataset on behalf of the user

[billschereriii]

Description

The fact that append_dataset() requires a user to have already put the dataset to the database is nonobvious, making this a tripping point for many users. Adding put() functionality to the append() call will make the method more immediately intuitive.

Justification

Clearer APIs will make it quicker abnd easier for users to learn to use this API

Implementation Strategy

Following an internal group discussion, this API method won't be changed. Instead, a parallel API method will be added:

void put_and_append_to_list(const std::string& list_name, const Dataset& dataset)

The idea is that having a separate API the does the put operation will make it more clear that this API method does not.

[billschereriii]

Updated ticket description with result of design spike and internal group discussion