Support for IMS service token generation plugin

[honstar]

Support for IMS service token generation plugin

Description

Adds s2s (service-to-service) plugin to support service token generation. This is currently WIP, see #34 .

Related Issue

#34

Motivation and Context

Currently, the existing aio-lib-ims does not provide means to generate IMS service tokens for service-to-service integrations. The proposed change integrates that support via a plugin analogous to the @adobe/aio-lib-ims-jwt one.

How Has This Been Tested?

100% code coverage via unit tests (jest) of the plugin that is being integrated. I've also tested this locally and validated the resulting IMS service token in an API call to a service requiring such a service token.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[honstar]

fyi: @moritzraho @shazron @meryllblanchet

[meryllblanchet]

Thanks for this great contribution @honstar !
@shazron @moritzraho could you have a look?

[moritzraho]

@honstar sorry for the delay, and thanks again for the contribution, I will have a look on monday