Use operation summary and description in generated function docs

[simonjbeaumont]

Motivation

For generated functions for each operations we generate reference
documentation. Currently this only states the HTTP information and the
operation ID, and doesn't include either the summary or the description
that may be present in the OpenAPI document.

Modifications

Change the reference documentation to include both the summary and the
description if they are provided.

Result

Reference documentation for operation functions contains the documentation from
the OpenAPI document.

Test Plan

The OpenAPI document used in the reference test includes operations with and
without these fields.

Resolves

• Resolves Include the user-provided operation description in the generated doc comment #64.

[czechboy0]

Thanks!