Improve code coverage

[diana-derose]

Goal :
To improve the test coverage.

Coverage needed in the following projects:
oauth2-platform-api
payments-api
IPP-Java-Devkit

Guidelines:
If adding a new file, please include copyright notice, sample here

[praveenadg]

I am going to take a dip at payments-api

[yjain3326]

I can take a look at oauth2-platform-api if this is still available.

[diana-derose]

@yjain3326 - Sure go ahead

[k-arjun]

I'll take a dip at some of the payments-api classes too.

[cho8]

Taking a look at the IPP-Java-Devkit tests

[tarungulati1988]

I'll add a few too. Will start with the interceptors.

[diana-derose]

Awesome!!! thank you all of you!