Design documentation added.

[janosmurai]

Type Of Change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Any modification in the test cases
• Any modification in the documentation

Checklist:

• I have read and followed the contribution guideline.
• I have checked to ensure there aren't other open Pull Requests for the same update/change.
• Every new modification in the production code has been tested.
• New and existing test cases pass.
• 100% unit test coverage achieved for every production code modification I made.
• I have made corresponding changes to the documentation.

Related Issue

Closing:
DEM-223

Description

Design documentation file added.