Add new SAP proprietary notice

[pombredanne]

See https://github.com/SebastianWolf-SAP/cloud-authorization-buildpack/blob/44e6d74bf3d9e40699fb8e9d84ebd54cc5e19d61/.reuse/dep5#L5

Disclaimer: The code in this project may include calls to APIs (“API Calls”) of
SAP or third-party products or services developed outside of this project
(“External Products”).
“APIs” means application programming interfaces, as well as their respective
specifications and implementing code that allows software to communicate with
other software.
API Calls to External Products are not licensed under the open source license
that governs this project. The use of such API Calls and related External
Products are subject to applicable additional agreements with the relevant
provider of the External Products. In no event shall the open source license
that governs this project grant any rights in or to any External Products,or
alter, expand or supersede any terms of the applicable additional agreements.
If you have a valid license agreement with SAP for the use of a particular SAP
External Product, then you may make use of any API Calls included in this
project’s code for that SAP External Product, subject to the terms of such
license agreement. If you do not have a valid license agreement for the use of
a particular SAP External Product, then you may only make use of any API Calls
in this project for that SAP External Product for your internal, non-productive
and non-commercial test and evaluation of such API Calls. Nothing herein grants
you any rights to use or access any SAP External Product, or provide any third
parties the right to use of access any SAP External Product, through API Calls.

This is used in many places https://github.com/search?q="API+Calls+to+External+Products+are+not+licensed+under+the+open+source+license"&type=code

@SebastianWolf-SAP which name should be give to this notice?

[pombredanne]

@qtomlinson ping, may be you know who to reach out to get input for a proper name for this license