Gather loan business logic behind a loan API

In writing a test script to automatically create loan, I've found a segment of business logic that could be usefully abstracted. Bundling this logic in a business logic module would save the clients from implementing multiple copies of the logic, and be less error prone.

Any client of the current loan API will likely start with a patron barcode and an item barcode. From the the client must:
1. GET the patron by barcode
2. extract patron UUID
2. GET the item
3. extract item information from item
4. create a JSON loan document from the extracted patron and item information and
5. submit that JSON loan document.

Further, the loan API trusts that the client is properly populating the item metadata such as title and location. A client could easily make an error in copying this data.

FOLIO will need to support both the 3M SIP and NCIP protocols, so there are two standard APIs that would benefit directly from not having to re-implement this business logic themselves.